I'm not familiar with the site mentioned by the OP, but there are a number of sites featuring amateur "straight" guys. Sometimes they jerk off alone, sometimes they jerk off with another guy--a stranger, a buddy, or even a brother or cousin--and sometimes they touch or jerk off the other guy a little bit but don't go very far, and other times it's an all out fuck fest.
The ones I've seen...I don't think the guys are actors. The guys seem nervous and are awkard in front of the camera, especially their first time. Some of them come back and do more videos and you can seem them gradually become more confident and talented as they gain experience. But many of them do one jerk-off vid and never come back. When the cameraman interviews them about their sex life and experiences, their answers seem spontaneous and genuine, not scripted, memorized, or rehearsed. I've listened to them talk about school, jobs, girlfriends, vacations, their buddies, what they like to do for fun, etc. Maybe I'm being naive, but it all seems real to me.
I believe these guys identify as straight. But as Arliss says, "they are straight as defined by LPSG." That is, as long as these guys are attracted to women, and may have a clear and definite "preference" for women, their ability and willingness to get it on with another guy doesn't threaten their straightness...at least not in their own minds.
Some straight guys are turned off by the thought of gay sex and would never consider having sex with another man under any circumstances. But I think there's a significant percentage of straight guys who are NOT turned off by gay sex. They aren't really into it, either, but it doesn't disgust them, and if someone pays them $1000 to go down on another guy, they're willing to do it.
Of course some of them are probably bisexual, but if they have a strong preference for women they may not feel any need or desire to identify themselves as bisexual. There's no advantage to them and it may actually be harmful to do so.
...I think the guys run the range in sexuality. Too funny though, they will be like, "Yeah, I never wanted to suck a cock, it is a turn off, but for another 20 bucks sure." Then you see this guy give the other guy this amazing blow job with expert oral technique and hungry for as much as he can get in his mouth...
I think the money is more than 20 bucks, at least on the sites I've seen. I've seen some where the guys seem to take to gay sex with great talent and enthusiasm. I've also seen some where the guys seemed very reluctant to touch each other and where the sex was lame and unenthusiastic.
For example, check out the preview on the page below. The preview is kinda funny, but I've seen the full-length video and it's
boring. The guys are so obviously NOT into what they're doing.
StraightCollegeMen.com - Dean And Trevor Preview - Straight Amateur College Men Jerking Off On Video
This preview from the same site is a bit better, but the guys are clearly uncomfortable and making :yuck: faces as they touch each other's dicks. In the last 15 seconds or so of the preview, they seem to get into it, and the action starts to get pretty hot. I haven't seen the full length version to know what it's really like.
I'm in no way promoting this site. There are better and less expensive sites of this genre out there. I use these as examples because it has video samples, and because awkwardness and discomfort of the guys makes me think they are authentic.