If he enjoys sex with a woman, then he's not homosexual, he's bisexual. But bisexuality is a spectrum.

There are bis who have sex with both men and women, but only have relationships with one. There are bis who primarily have sex and relationships with one, but do have rare instances of being with both. Etc.

This guy isn't like gay men who marry to hide being homosexual - they might develop a platonic love for the woman they marry, but the entire romantic and sexual aspect of the relationship is an act.

This guy is someone who never had any romantic or sexual interest at all in women so he thought he was gay. Then he stumbled across a woman who looks like a man, and romantic or sexual interest developed along the way, so he tried PiV and liked it.

If they break up, I doubt he'll go looking for another woman - he was never interested in them before. He just happened to like this one because she looks like a guy. He's technically bisexual, but he's on the far edge of the spectrum. Where he's into men 99% of the time, but will dabble a little bit with women under the right circumstances.

Notice in all their talk about finding a "cis gay man" who loves their "bonus hole", you never hear about the "cis gay man" eating pussy? These kinds of bisexual guys aren't into it for vagina, they just enjoy sex.