I'm going to go counterpoint on this: I don't think he's repulsed by sex with women. I think the truth is probably more prosaic: When Phail was a younger man -- high school, college, perhaps some post college -- he was not a man that was attractive to women. So his opportunities to have the experiences that most of us have starting in high school/college weren't there.
I've known guys like this. Eventually constant failure creates a mental feedback loop where as much as they want to have sex, he's unable to have it because women aren't interested. After a long enough time, a guy off-ramps from that loop and can just become disinterested in sex, and even romantic relationships, because their formative years didn't allow them to gain the experience -- both physical and mental -- to have functioning relationships.
But with Phail it becomes mildly more complicated because although he's now no longer not interested in the physical and mental relationship, he still wants the status that comes from it. So you have Leanna and Khet come in, one of whom obviously wanted an actual relationship while the other is a bit more unknown, and and give Phail that status. For Leanna, the appearance of a relationship wasn't enough and she ultimately left after she matured enough. Khet? Well, as much as we like to create canon surrounding her and what she thinks, we don't know what she really wants or doesn't want. Clearly at one point she engaged in physical and romantic relationships and perhaps expected that with Phail.
A lot of words to say, I don't think Phail is repulsed by sex with woman, I just think he reached a point where it no longer interested him because he never had the chance to have it.