This is a good point. My 3lb chub (I just learned that term I’ve been dying to use it) has nearly a pint of pure fat. It’s hard to imagine a scenario where a pint of fat isn’t going to leave a good sized pool of fat in my dutch oven.
Another variable worth considering is the amount of water present. The lean portion of the meat is still 90% water. I know with chicken that they inject salt and water up to something like 10% by weight to increase profitability. It’s possible the same thing can be done to ground beef.
When I was meticulously tracking calories, I used to cook the hamburger, drain the liquid and separate the liquid in a gravy boat. There was a ton of broth. I’d then weigh out the fat on a food scale and add the same number of fat grams to each portion.
I’d be curious to cook 1lb walmart vs 1lb whole foods hamburger in a sealed container so no liquid could boil off to compare the difference in residual broth and fat.
My guess is that the walmart ground beef woukd have a higher fat content and a higher broth content. It’s hard to imagine walmart could sell 73% hamburger for $2.00/lb without adding extra fat and water.