The comment was about teeth, though, and flour/meal is abrasive, though. Not to the degree it was in prehistoric times--dental health went to hell during the transition to sedentarism, thought mostly to be due to milling introducing rocks etc. to the meal--but, setting aside that both are nutritionally probably not great, it stands to reason that the stuff mentioned in that blog post (mostly grain-derived) have more ways to stick to the surface of teeth and hang around to mess up mouth pH.