The study you're referring to does not claim that this difference in brain structure or chromosomal arrangement is common to all gay men, merely that it may be observable in some gay men.
You are correct, it does not(though the study pointed out that it's more common than not--at least within the parameters of the test group), and that is perhaps one of the most intriguing factors of it, at least to me. As I *was* answering the question originally asked, more specifically I was answering the one which I quoted.
I was pointing out that perhaps because of this, some gay men are effeminate and some are not. The ones who show these effeminate behaviors and thinking patterns would be the ones with the difference in brain structure, although they could also be adapting a particular behavioral pattern because they think that's the norm for gay individuals/want to fit in/etc as has been suggested, and the ones who do not fit the effeminate stereotype of course would be the ones with normally structured brains, or those who just don't conform to stereotypes.
A biological psychologist would tell you it was due to the biological reasons as stated above, a behavioral psychologist would say that it was due to the behavioral patterns as stated above, and an intelligent psychologist would state that both are probably factors of why there are effeminate gay guys. I'd go with option three.
As you pointed out the test group was small and the findings not entirely conslusive, though the theory is interesting.
Yes, quite interesting. .
Of course, sexuality in and of itself, and the reasons behind it, are far more vast than a simple biological, behavioral, or societal explanation can cover.