If that were the case, they homosexuality would be limited to certain cultural enclaves, say Hebrews or the Greeks, rather than being evenly distributed across all cultures/races/sexes.
Also, the claim that 'bisexuals' account for more people self-reporting as 'gay' in nonsense, as most people will, given a free choice, will select the easiest choice. If you can marry a man and face losing your job, your home, your career and your family, or settling with a woman you're equally attracted to, three guesses what they'll do. They'll go with being straight, rather than being gay.
Ah. but the thing here is even the "gay historians" who have brought to light all of the "homosexuality" that went on in ancient times seem to like to conviently overlook the whole matter that a lot of that "homosexuality" they found wasn't homosexuality at all, it was bisexuality being openly demonstrated. Slightly different critter.
It also stands that if you go with "sexuality being a spectrum" and the possibility that there are a multitude of genetic triggers that are "indifferent" as to gender that influence sexuality, as well as a number of others that are "keyed" to specific gender traits, you then end up with a very broad "sexual spectrum" indeed.
Which would also make it hard to pin down the "sexuality gene" because there are many different genetic routes that can result in someone with a certain specific sequence reporting as Hetero/bi/homo-sexual in their preferences. As there isn't actually "one gene to rule them all" when it comes to sexuality, but rather several, and not all be created equal. Which is also something we know about from genetics, as we have the "simple" dominant, and recessive traits. Then we have the even more complex "recessive traits" that rather than being reliant on one sequence alone, they could be relying on 2, 3 or even 4 other genetic sequences lining up in just such a way. (Human Eye color is one such an example of 3+ different genetic pairings deciding eye color between Brown, Blue, Green, Hazel, etc. And unlike eye color, in particular if you're dealing in bisexuals in particular, you don't have a solid independent reference point to start from in any genetic study. You can take a picture of the person's eye in order to validate their reported eye color. As to "independently validating" their self-reporting as to their "innate sexuality" rather than their current sexual preferences?(Which probably have been "socially influenced") Good luck.)
Nothing about a "natural predisposition towards bisexuality/heterosexuality" rules out the "homosexual" outcome if the bisexual population is substantial(or even the majority in reality). If you're male, and you find you're physiologically attracted to some/many/most men in a sexual way, then you're sexually attracted to them. It isn't much of a choice. Now if they also are attracted to women as well, ok, well, then they have something of a choice. But as I'm arguing the position of "sexuality as a spectrum" (How 1950's of me) even that may not be much of a "choice" for them, if say on a scale of 1(low) to 10(high) their attraction to men is an 8, while their attraction to women is a 3, how do you think they're going to report their sexuality?
You're also ignoring the matter that while the LGBTQI+ crowd likes to talk big about "being inclusive" the reality is that by most reports, if you're Bi, be prepared to be treated like dog shit by the homosexuals.
"A Bisexual is a homosexual who cannot make up their mind."
"A Bisexual is a homosexual who refuses to get off the fence"
"A Bisexual is a homosexual who is trying to get the best of both worlds."
"A Bisexual is a homosexual who is afraid to come to terms with their sexuality."
"A Bisexual cannot be trusted with anybody."
And the list goes on and on and on in today's society.
Oddly enough, it seems to be the Gay community in particular that likes to push the "binary" sexuality idea, you're either straight, or you're gay, there is no in between. Which gets back to "social pressure" inducing people to claim sub-optimal positions as to their own sexual preference, either knowingly or unknowingly as the case may be.
Edit: It also is probable that a number of the "cured homosexuals" weren't actually homosexual in the first place, they probably were bisexual. So in some respects they did have a "choice" in the matter, although the underlying physiological bias towards a same-sex preference undoubtedly still remains.