I always take that question as more "I'm same-sex attracted, do you hate me?" more than "I literally think I am literally bisexual, does that sound right to you?" They're more fishing to gauge my reaction to the confession of same-sex attraction.

I think when I take it in stride and don't do whatever they're afraid of, it gives them more confidence and makes them feel safer to talk to other people, especially gay men.

Again, this doesn't bother me. There's a difference between kids navigating possible social rejection with identities and grown adults scamming people by intentionally lying. I do remember picking up a bizarre 1940s-era book once at a used bookstore about the epidemic of "bisexual" men at the time who cheated on their wives with other men. I should have bought it. I bet if you read between the lines they'd mostly just be gay.

The gay men who refuse to believe bisexuality is real because young gay men lie about it so much are just self-centered. It ain't all you! The label wouldn't exist for you to use in the first place if there weren't real men like that.