This debate over whether someone is really one thing or another always muses me. I, like mikeyank, have always had a very specific preference for young men of a certain appearance who engaged in gay sex but were straight. Of course, I have no way of knowing if any of those guys were truly "straight", I just reacted to the persona and for all I know, they went off to see other guys who tossed their legs in the air and pumped them like they were paying for it.
That said, a few observations. Over the years I have represented a number of working boys on a variety of charges related to their careers. There were two I represented a number of times with whom I have stayed in contact over time. Both of them stated they were heterosexual when they were working but both bottomed regularly. They did this for two reasons according to the two of them. First, they were very masculine and straight appearing street guys and it excited gay men who had fantasies of fucking a straight boy. This meant they could barter away their virginity a number of times and at higher prices than other sex acts would bring in. It also according to one of them meant a faster turnaround time because most all the guys who wanted to screw him were so excited about the idea, they came very quickly. The second main reason why they did these, was that having sex with men was not really super exciting to either of them. It was harder to get hard and stay hard so it took longer and time is money.
The other issue that exists s a simple one. This is not a black and white issue. It is a spectrum. Kinsey proposed that years ago and everything I have seen since then seems to support it. I have spoken to a lot of younger guys. First, for most of them, they really do not make a big deal out of the gay/straight dichotomy. It is irrelevant to them and many of them [not all] admit that they have fooled around on occasion. Some more often than others. Most said it was fun but not as much fun as women. Then there are those who say right up front that they like sex with both women and men. They might prefer one slightly more than the other or not, but they enjoy sex with both. The stigmas that existed in my youth in the 50s and 60s no longer are as strong. That's a good thing. They needed to go.
But they also mean that the young men willing to go into this line of work now are quite different than the boys were back when the Athletic Guild or Old Reliable were pumping out the photos and film clips.