How is it not bisexual?

I find labelling of sexual preferences a bit tedious. Having labels can be handy when they serve as a shorthand, but sexual preferences have all kind of identity-building connotations.

So, personally I think someone who identifies as a man is attracted to other men for any kind of sex, that's gay. Having preferences for what particular kind of sex doesn't change that.

I know a lot of people don't feel that way. For a lot of cultures and people what makes it gay is a man being poked with a dick, whether that's in your mouth or ass. That's why when they are trying to figure out risk for diseases they ask if you've had sex with a man, not if you're gay.