Beyond the simplistic and regressive discussion of sexuality being inferred from the type of performances that sex workers engage in, let me offer an alternative hypothesis as food for thought.
A YouTube search of Dawson's "real name" results in a video of an award that he won for community service. I would propose that his acceptance speech reveals an underlying motive that many rarely discuss among G4P performers. He noted that he faced a lot of social rejection as a child due to a speech impediment. It is not a far leap to infer that being complimented on his body must have been especially meaningful for a man who faced such early condemnation. In fact, trying to please a charismatic producer who accepted and admired him, must have been the perfect recipe for creating a porn star. Men who were once scary and mean suddenly approved of his body and encouraged him to do more. It didn't matter that he didn't see himself involved with men in an intimate relationship in the future, because the adulation made him feel good.
One is never certain if these ongoing questions are just a way to engage others on this board, or if there are still people nieve enough to not know how sexual identities are formed, but I hope this alternative explanation, written with good intentions, explains some of the reasons that straight men get fucked on video for relatively small rewards.