If you ask someone whether he is gay, and he answers you yes or no, you haven’t really learned anything. You haven’t learned if he’s ever thought about having sex with another guy. You haven’t learned if he’s ever actually had sex with a guy and discovered he didn’t like it.
Sexuality is a broad, expansive spectrum. People rarely dig deep into what theirs is for just anybody. If you ask, you’re just looking for him to label himself for you. Labels are meaningless when it comes to this kind of thing.