The enlarged 7th interstitial nucleus found in cadaver studies, and trumpeted as the genetic link to homosexuality, could be enlarged (hypertrophied) through use, similar to the growth of exercised muscle tissue.
You may recall that the cadaver studies were performed and published by a practicing homosexual.
Sometimes, "I don't know" is the best answer, specifically regarding the nature vs. nurture argument of homosexuality.
Faith is useful for the many "I don't know(s)" of life. I believe that homosexuality is unbridled lust, since it can be "controlled", unlike other genetic traits.
It has been said that the highest praise of God consists in the denial of Him by the atheist, who finds creation so perfect that he can dispense with a creator.
Marcel Proust
I did state Darwinian or Divine "survival of the fittest" it makes sense either way.