No man thinks they are same sex attracted when they are not. It is difficult and potentially still dangerous to come out - why would you do it with 0 sexual attraction to other men.

Will caveat, I'm not a guy so I don't know how common this is, but I have a friend who is straight and GNC who, when he was a young teen, was told constantly by people around him that he must be either gay or bisexual just because he was GNC. If OP and his friend are very young, perhaps it's a possibility with his friend?

He is gay with internalised homophobia, and perhaps calling him a faggot is not helping... He is so uncomfortable he is going to say he is incapable of feeling anything for anyone ever, rather than admit he likes other men. Being gay and in particular gay sex is still stigmatised, it can also be a terrifying prospect and I suspect thy see two are very very young.

That makes a lot of sense, as well. I've heard many stories of young LGB kids/teens doing this.