I agree with most of this. However, I think it is worth noting that JKR's understanding of biology is about as good as her understanding of math or astronomy so I don't expect her to have even thought of this sort of thing. I don't think the nature of complex adaptations is a great argument in this context given that we've already found that magic doesn't seem to act very much like what science tells us to expect in general.

While I support Eliezer's right to do what he wants, I suspect that Harry will turn out to be wrong about this, and that we'll find out in the story.