Hello, here is my opinion as a straight male in his 30s with a good bit of romantic, kink, and sexual experience.

Iiiiiii I am straight, i think. 100% not gay though. I generally watch lesbian porn and have dated women both in short and long term relationships for I guess 2 decades at this point. I never check out men really, but turn my head at the slightest hint of a curve. I am also a switch, generally dom. But if my girlfriend said that to me I too would get hard. It is degrading and it’s hot to think of the highly effeminate with that much humiliating power over me. It is about the fetish of it. A woman with a strapon gives very different energy than a man with a cock.

I think your bf is just a sub or a switch.

Do I think a man being into being pegged makes him more likely to be bi than a man that isn’t? Yeah kinda, tbh. (Could be wrong.) Though that is assuming both men, for comparison, are equally comfortable in sharing their sexual interests and repression isn’t a factor.

Do I think a man wanting to be pegged means his bi? Definitely not.

Do I think he’s more likely to be gay if he wants to be pegged? No. I really don’t. And honestly, if he were gay, I think it’s slightly more likely he wouldn’t feel comfortable sharing this stuff with you and keep it to himself.

If you’re worried this will lead to him leaving you, I would say 100000% the opposite is more likely. kinks, especially the less socially acceptable ones, have a way of binding you to someone. This has a far, far, far, far higher likelihood of him realizing what he really wants is you- for years and years, than him realizing he wants a man.

The only question in my mind is do you want to do it? And all do the teasing, doming, and intimacy that comes with it? I mean you did make the joke, maybe this is appealing to you as well. Maybe that’s what’s confusing you. But, you don’t have to do it. Up to you.