In my opinion, and I realize it's just my opinion, if a guy just likes the sensation of bottoming or just learns to tolerate mainly for money -or even likes it so much he gets a dildo and uses it off the clock-but would never get with another male off the clock- that's not really bisexual to me. I mean assuming I could keep an erection-I'm assuming I'd enjoy the feeling of a woman stroking me off. That doesn't mean I'm bisexual.
But no matter if they called themselves straight-the fact that they wanted to have a regular relationship with you, would, I think, imply that they enjoyed being with you as a person and on some level enjoyed man-to-man sex = bisexual.
Gman