This is a fairly straightforward matter of whether his statement is right or wrong, I don't think it's fair or helpful to describe it as "particularly arrogant".

I agree that in general, people's understanding of human physiology tends to be simplistic and wrong.

But Dustin's description here aligns with what is generally known and accepted, and he doesn't venture details beyond what anyone with with a sound understanding of physiology could reasonably claim to know.

If he's wrong, that would be easy to prove, in which cas you should do so, so he can amend his post.