[necovek]

I think that hypothesis can work for many other things (eg I can imagine high myopia to be an issue for hunter-gatherers), but not teeth or bones: what we know of primitive societies and their eating habits is from looking at their bone remains and tools. Hopefully scientists having access to actual findings are not overlooking child skeletons with bad teeth when coming up with conclusions that our primitive ancestors had better teeth.

[TopHand]

It is my understanding that only about 6000 ancient human skeletons have been found. https://humanorigins.si.edu/evidence/human-fossils Many of these are incomplete. So the samples of children with bad teeth could easily not exist or be very limited. The same could be said for children with good teeth.