The focus of the question could be changed, observing instead that "feminine-acting" (i.e. what we sometimes call stereotypical) guys are, I think, USUALLY gay. Yes, NOT always, but certainly far more than 10% of "feminine" guys (compared to the common wisdom "10% of the male population is gay") would be gay. And those who act the most feminine are most likely to be gay among that group of men who act feminine to some noticeable degree.
Which skews the total population of gay men (as averaged out) toward seeming to be more feminine - if somebody were to take the entire male population and, individually, calculate some numerical measurement of "feminine" conduct and determine if every male was gay.
It's an impossible study, though, because it would have to include bisexuals who are mostly gay. So, would those who consider themselves 70% gay be included, or would it need to be at least 85%?
Most people who consider themselves gay - and validly so - are actually bisexual, though their gay percentage may be 93% or 98% or 99.5% or something. For that matter, the straight dude who wants the occasional blowjob outside his marriage a couple times a year doesn't become gay just because of that, but he IS bisexual - perhaps 97% straight or something. But he also knows what feels good...
The feminine traits would be averaged across the ENTIRE populations of males, and the population of those who identify as gay, and the average "femininity trait numerator" (or whatever in the hell the number is called, lol) would have a higher number in the gay community.
The question "...ARE gay men more feminine than straight men?" COULD be read two ways:
1. When somebody is gay, why does he act more feminine than a straight guy?
2. Averaged across the entire population, why is a gay man more likely to appear feminine than is a straight man?
I read the question the second way; the first way would indeed be assigning a stereotype, which has been proven over and over to most often not be true. I don't think the question was asked in a "stereotypical" way at all.
I guess after much thought, if I was asking the question instead, I'd ask it something like "Why IS a gay man more likely to appear feminine, than a straight guy is?" But it would be very easy to ask the question the way it was asked, and that's how I took it, and if I asked the question without pondering for half an hour exactly how to ask it, I might have asked it exactly the same way. I'm not going to pile on the OP for this.
OK - on the AVERAGE for the populations, I'd say YES. However, sometimes people consider the MEDIAN, which I don't think works here.
Hypothetically after all the statistics are compiled IN THE UNITED STATES (where the OP most likely lives), and let's say there are 100 million adult men, of which 10 million are gay...find the 50 millionth guy along the femininity scale, and find the 5 millionth gay guy among the femininity scale, and compare the two. They would be INDISTINGUISHABLE from each other.
I specify the United States, because that's where 99% of my experiences are, and population/cultural differences may lead to different answers in other countries.
We all know that it's only a fairly small minority of gay men who appear to have "easily visible" feminine traits in their daily actions (or speech, etc.), so those gay men would entirely escape the median/middle, but they bring up the average.
Why does my mind have to be so damn analytical, anyway? I'm supposed to be doing other stuff right now!!
And NONE of this answers the OP's question at all, either.