Exactly. Of course, similar happens with various kinds of food. Once I have read that a ripe, sweet pumpkin has 7 times as much carbs (therefore calories) than an unripe one. Apples aren’t like other apples or the same apples later when they lose water… 
That’s little but what if I eat very unripe, small pears in a curry? And what if I make a complex soup with all the weighing but end up eating some that can’t represent the whole so well (less vegs, more liquid, maybe more meat as well)?
At least if my meat loses fat, I can weigh it, there are methods where it’s not the case…
Stricter carnivore is easy to track as there are so few items - it’s just less accurate if one eats fatty meat. But why would it matter? I am very happy with the knowledge I ate a decent amount of meat and little else (when that happens… usually not but I get better), it definitely helps me with fat-loss way more than more accurately tracking zillion kcal on a carbier day… I still like to see approximately how much I ate, to analyze what I did wrong again. Right now, I track to see if my low dairy efforts work. I know they do but is it true even in the presence of pork shoulder…? I know I need to eat lean meat too so I do that but it’s SO easy to overeat fat and protein, I must be careful. Other people could have stopped tracking ages ago, I do it even after several years. Even with inaccurate fat grams, I get a pretty okay guess for protein and it helps.
Nope, it’s not enough. Pure meat pork shoulder is still fatty.
And good luck to separate fat in certain meats There are tiny layers, marbling and whatnot… I wouldn’t even like to trim the fat from the rabbits we eat and I must say, it’s a fat rabbit, it has a significant amount. Chickens can have even more but there the bone/skin/whatever makes tracking a nightmare anyway. I do trim the fat when it’s a too fatty chicken, last time I got a small glass of schmalz from that and the skin.
When it comes to fatty meat, I usually take a guess. I think I wrote about my sensitivity. Before I had my training, I automatically ate 65% fatty food. If it was lower, I added fat, if it was higher, I felt it’s fattier but still liked it, usually So I often eat, like, pork shoulder or pork loin and track it as pork chuck as it has about the same fattiness in those cases. Right now my pork shoulder is as fatty as usual so I trust the database (I mean, use it, of course I know it will be inaccurate. I don’t even know if the average pork shoulder I ate is like the database… but both shows very much fat, good enough :D) and track it as half shoulder, half chuck as I rendered out the right amount of fat for it… It can’t be too far 
Being off by a few hundreds of kcal on some days (and less on the others, I try eat as lean as I can, after all) is still accurately enough in my world. I am WAY more inaccurate without tracking and as I wrote a few times, protein is very important for me as I take minimizing it very seriously since some time.
But I start to feel I wrote too much about this… Interesting topic though. Sometimes I mention it to people on the CICO site I use for tracking when they get shocked they went ONE gram over their fat macro… I went 100g over my fat macro so many times, okay, that wasn’t necessarily good… But that is 100, not 1. I can’t even track nearly that accurately, I surely am off by 10-20-30g fat quite often… But that’s not much and tracking doesn’t cause fat-loss anyway.
Full trimming, maybe but even that is individual, some people love pure lean meats. I often eat green ham as it’s cheap and lean and still can be nice… But the joy and even the edibility jumps if I eat the fattier parts so I do that… And my SO eats the parts with zero visible fat (I make very sure all the visible fat ends up with me) and he loves it. He starts to complain around pork chuck level (he still eats the leanest possible slices in a pinch) and wouldn’t touch pork shoulder or pork belly.
A trimmed meat can be exactly like a normal cut, I buy “sausage/scrap meat” sometimes and that has pieces of green ham with a big fat blob attached… I prefer marbling or finer layering, not that, I cut that off and make skinless scratchings. Maybe I leave a bit if the meat part is too lean but alas, super lean meat never will be great, no matter how much fat I add. It must be with it from the beginning. But it still helps a lot.
Once I bought “pork loin”, the cut I used to avoid due to being super lean for me (and that’s the normal kind, not the light version with truly zero visible fat)… And it was about pork shoulder level fatty… That needed a lot of trimming! But I probably liked the result while my SO didn’t
Some lean meats have better texture than others and anyway, juiciness helps. I do love fat for flavor (it still doesn’t mean much is needed for a meat being tasty) but I very much love lard too. My SO dislikes it.
So… It’s about the fattiness level for me. Too low, I add fattier meats or at least something flavorful. Too high, I do some trimming, before or after cooking.
That is the one I keep forgetting But I weigh the same for years anyway so it has no point. I do weigh myself but never in the morning or without clothes. By the way, clothes are more reliable and easy to me. I couldn’t care less about my weight except I know I can’t keep the current one and look okay.
Just seeing I weigh almost more than ever year after year doesn’t help me, tracking may.
But again, tracking isn’t about our weight only… Some do it for carbs, I focus on my protein intake in order to keep it as low as I can… And I do like my numbers. I even suspect tracking become something that helps keeping myself in check (I am still too wild but it would be worse without). I hadn’t it in the first several years of tracking or just lightly and not because of the tracking, per se but now it does help just like being in the carni thread helps.
I won’t track anymore (well maybe sometimes especially on experimental days but it will be a few times per year or less) if I ever slim down. Not like it seems I will ever able to lose fat on keto but I haven’t given up all hope yet. Actually, losing tracking should be a great motivation to lose fat, alas I never functioned like that. I can’t restrict myself just due to some way less than life or death motivation…
Numbers can be nice. We (my SO and I) track various things. We have detailed data about our energy consumption. Because we like to look at it. Mostly him nowadays but I have my curious moments… We like to know how much our machines use up. So yep, it can be kind of a hobby stemming from curiosity but it does help at some point.
Other people love to track how many food items the birds brought to the nest I wouldn’t comb over the night video to get it but some do and I like the info… Many people like numbers. If I could, I would gladly see how much I eat and use up but alas, I only can track my consumption but not every day and it isn’t accurate. Normal tracking is a chore enough (but I still can’t stop for long) but there was a month when I made a spredsheet and got my average egg, processed meat, dairy etc. consumption per week. It was educational but I never could bring myself to do it, thankfully now I know it accurately enough: the mentioned ones are little And when not, I see that. Once I wanted to see how grams of what kind of meat I ate in a whole month but couldn’t do that. It seems simple though, I only need one measurements per slab unless my SO eats some but that’s not much extra work. But I know I eat about 95% pork anyway and about a pound a day. No need to know it better, it just would be mildly interesting, you know?
Not as interesting as my extreme macros. I like to know my lower and upper limits. And my lower limits for longer term while still feeling okay. And it’s fun when one of my macros double from a day to the other. I don’t want that so I may be not pleased but no harm is done if it’s occasional and it does entertain me for some reason.
) So I’d add, it’s also impossible to stay clean if you shower every morning and then dive directly into a mud (or chocolate) puddle every few hours. 