Oh, I don't think so.
I don't have any n=20 psych undergrad studies to cite on the subject, but I do have a reasonable degree of firsthand experience with gay men, in bed and out, and it's that experience which gives me to espouse the conclusion you quoted. That conclusion is also not unique to me, or for that matter even original; the man from whom I first heard it, quite a few years ago now, is not only himself gay and much more widely experienced than I am, he's also a great deal more intelligent and insightful, possessing a widely accomplished intellect and the postnominal letters to prove it. He and I have disagreed, whether seriously or for fun, on almost everything - but nothing I've seen gives me reason to doubt this claim in particular.
I get the impression that "narcissistic" in this usage might be read as some kind of denigration, as though I'm alleging that all gay men have a personality disorder. This is not the case. If anything, I think it's just that the focus of our sexual interest, specifically on people who much more closely resemble us than is true for straight men, tends to intensify what I might describe as the narcissistic aspect of male sexuality in general - and, again, the word "narcissistic" doesn't imply a disorder. You don't need to fall in love with your reflection to find worthwhile looking in a mirror every now and again.
That's quite a bold statement. Can you elaborate more on this or provide some evidence (honest question, I'm not trying to get into an argument)?