Defining yourself by your gender identity is not delusional.

Is defining yourself as a wolf delusional? Is defining yourself as a child when you're an adult delusional? Is defining yourself as black when you're white delusional?

Again, what you think doesn't matter one bit to reality. I don't want to grow up. I want to have a tail. I want to fly. Too bad!

If a man with gynecomastia cannot show his breasts, is it due to being female?

I don't understand. A man with gynecomastia can show his chest, that's the whole point. Women cannot show their breasts because they're women. Even when a man has gynecomastia that makes his chest breast-like, he can still show his chest. Some women lying that their breasts aren't breasts and trying to haggle that they specifically shouldn't have to deal with misogyny because they're special does not for a moment change the fact that they cannot show their breasts because they're women, and breasts are not allowed to be shown in public because of sexist double standards. Some women wanting special treatment where they're free from misogyny due to "not being like those other girls" is ultimately irrelevant to the fact that they're going to experience it, just as any woman is going to experience misogyny whether she insists that she doesn't or not.