A feminine man is far more palatable to heteroflexible men, therefore more likely to arouse certain feelings and ideas in them. But here I am not strictly referring to feminine clothing or makeup, I am referring to physical features and stature as well.
Being slender, smooth, fair, longer hair, pretty, shorter than them, it all lends itself to a path of least resistance.
There is no one thing that makes a seduction. You could have all of the above, and still be ugly/unattractive to a heterosexual man.
I enjoyed my androgynous years thoroughly, and it was certainly magnetic to heteroflexible men. Equally though, it attracted a lot of homophobic men as well. A double edged sword if you don't know how to handle it.
I get your theory but I don't think it's necessarily the case. I'm a 6'3 hairy, masculine viking of a man. lol. Pretty maybe, though. ;-) A lot of the straight guys I've been with are also not traditionally 'fem' or anything. Sometimes I think it's just the idea of great sex that turns a man on and probably in my case how open and relaxed I am. If I want something, I make it known. I think that kind of simplicity is a turn on for a lot of straight guys and probably helps the sort of guys who have considered experimenting before to relax and get into it. I could stroke my ego and say it's my stunning looks, brilliant personality and sexual prowess. Instead, I prefer to be humble.