There are no conclusive studies, but there are credible hypotheses and studies in animal models that suggest sexual orientation and gender identity (as well as other neurological factors) may be impacted by prenatal exposure to hormones and endocrine disruptors.

The science is a long way from having conclusive evidence either way, but there is a reasonable basis to think that it might have an impact, which should urge caution. If we found a new material that looked a lot like asbestos under a microscope, you'd presumably limit your exposure to it until proven safe?

Yes, prenantal exposure to hormones is one thing but I was specifically referring to GP's frankly controversial implicit claim that gay men possess lower T.

Anyway if I recall correctly that research suggests that higher prenantal T exposure increases likelihood of homosexuality, the opposite of what stereotypes might suggest

Its the opposite of what you may think. High T makes you more sexual and less inhibited. Many, many, many, many people turn to the dark side after using anabolic steroids. Even if they don't become full Sith masters, they often still like to dabble in dark side of Thailand.