Touche. It is possible to explain almost anything ex post. Moreover, it's really unclear (and what I've read does not address) how a gene that causes someone to not reproduce gets passed on. Assuming that just you have the gene and your relatives don't, it's beneficial. But if you all have the gene, that's a very different story. A gene that causes me to sacrifice myself to save my brothers is conditional - it doesn't matter unless the need arises. A gene that causes me to prefer non-procreative sex doesn't seem conditional in the same way - it simply prevents me and anyone who has it from reproducing.

In short, while one can rationalize the behaviour as advantageous ex post, it's rather hard to actually put that together cogently, and it's a very long way from getting rid of, "largely accidental" as an alternative explanation.

I will admit bias on this issue, having dated a woman with a lesbian identical twin.