I think the issue is that "female" can refer to any species, whereas "woman" refers only to humans. So when someone obliquely refers to women and someone responds "oh, you're talking about females!", the subtext is that they have now realized that we're talking about women, but haven't quite realized that women are people too.

It would be the same as calling someone a "human" rather than a "person". Like aliens do in the movies. Maybe you don't feel that's dehumanizing, but I think a lot of people would.

(Classicist pet peeve: A word's etymology has nothing to do with its modern denotation and connotation.)