I never tried anal with my past women so I don't know about the experience. However, I cant say a dude is gay if he does anal with his women.
To determine if he is a homosexual, it depends on his sexual orientation and behavior. He would have to be attracted to the male anatomy. Does he get aroused by another man and his presence and body like we get aroused by fine women? Has he had sex with men before? That would make him homosexual.