The entire premise here is STRAIGHT GUYS having gay sex for money. I have met more than one straight guy in my life who did that. As one put it to me, he hated 9 to 5 jobs for shit wages, he was a lousy thief, he was not interested in other forms of criminal activity and getting paid for sex was easy work. I cannot and do not speculate on the actual sexual orientation of people performing here. I do not know any of them personally and some may well be bisexual or even gay but I do not care so long as they do a good job when on camera.
That said I do know that some people, both gay and straight, assume any man who engages in homosexual sex must be gay and they are always happy to inform the person so engaging of their opinion. So I can see where a model wants to establish emphatically that he is doing this work for money. I do not think that makes them homophobic nor is it offensive per se.