Provide proof of such allegations to back up such a claim, and yes, I’ve heard of these speculations many times.
In general one example is thalidomide. It produces non-genetic but still congenital birth defects.
As to specifically homosexuality? I have no idea if it is genetic, non-genetic but congenital, post birth mental defect or a choice. I wouldn't be surprised if it is a combination from all of those and more. I was just refuting the author's erroneous assertion that all birth defects must have genetic causes.