Not the person making the claim, but it's more like 3g with TEF taken into effect, and combine that with the satiating effects of protein, it isn't very likely that people are going to eat 2000+ calories of protein. Even if you consume it in vast quantities like many bodybuilders, 300g of protein is only 1200 calories, ignoring TEF. Eat 1200 calories of protein and see how hungry you are for even more.

Not quite "negligible" but food for thought. (pun intended)