Normally I'd let cute guys (seriously, you should consider starting your own OF) believe what they want to believe but not this one, gays need to stop propagating the idea that gay for pay doesn't exist, because it does.
Sexuality is not defined by whom you do the deed with but by whom you're aroused by. And there's actually have a test for that, they let people watch lesbian and gay porn, bisexuals would be aroused by both, straights will be aroused by just lesbian, and gays by gays.
How do they keep their dicks hard you ask? Fluffers! They may have women who would help them keep aroused on set, or at least straight/lesbian porn. Take this clip by Hardvalentine as an example,
https://monstercockland.com/292165/hardvalentine-and-sean/ he's being sucked by Sean while visibly looking at the straight porn next to him.
Then there are those straight guys who bottom because they can't keep their dicks hard for a guy
https://www.queermenow.net/blog/elliot-finn-gay-porn-tiktok-mason-lear/
There are also exhibitionist straight guys who get aroused by the attention, it doesn't matter if it's from a guy or a girl and it's more common among strippers, obviously.
Labels are just that, labels, it doesn't mean they're actually attracted to the same sex. For a short while, I identified as bisexual despite never wanting to do anything more than flirt with a girl (which I later learned has more to do with my desire to have control over people) simply because I was afraid of the gay label. Lucas may have something similar, with the only difference being he's afraid he'd lose some of his audience by saying he's straight. We don't really know what's happening behind the scenes, for all we know, the cameraman may actually be a naked woman helping him get aroused.
The bottom line is that sexuality is more complex than the labels people identify as.