remember everyone's growth is different. there are too many variables. im not sure if im on board with the mouth breathing claim, that in and of itself shouldnt cause lasting damage. however mouth breathing could involve a tongue thrust and that can mess with the teeth and palate development. to what degree again all depends.
also, you can experience abnormal growth and the class of your jaw may not change. the bite can also be superficially corrected with braces but doesn't undo the damage done to the rest of the face.
Now, diet is probably very important. I'd say eating properly as a kid increases your chances of developing correctly. But these blanket statements like "all", "every", "never" etc are ridiculous. And if a theory can't explain all results, then it simply isn't true. It might not be entirely false, but sound science has to explain every case. The only way to do that, with jaws, is to admit phenotype = genotype + environment. It's both, and my guess is that the affect environment has over phenotype is determined by genetic predisposition/sensitivity.
we can't get too hung up on the generalizations. it doesn't at all take away from the very real fact that the human face is incredibly vulnerable to the environment during childhood.
the jaw is just one feature and isn't always affected by abnormal growth. the bite may be preserved but the jaw itself could be underdeveloped.
i dont think diet is that important tbh. pacifiers/oral posture are the worst, most decent dentists and ortho will tell you this.
@euphoria
as far as the cheekbones go, what we do know is their development is tied directly to the upper jaw.
