I kinda wonder if the fiber thing is a lot like the vitamin requirement thing in that it changes dramatically according to what you are and are not eating.
Vit C requirements are drastically different from a carb burner to a carnivore. I’ve been told antioxidants are similar. Could fiber also be similar? Maybe context matters here, perhaps more so than has been really studied?
I don’t know, it’s just the thought that came to mind.
FWIW, I don’t worry about fiber. I do get some. I happen to like a little veg with some meals. I like an avocado pretty often. Berries can make tasty condiments. And things in the “lower regions” are working just fine. And life goes on… 