Not who you asked, but I feel it's more of a social thing in myself. HRT has biological effects, but I don't think I'd be doing it in the first place if gender wasn't such a construct to begin with. I believe the sexuality changes are mainly social as well. There's the transmasc meme that T makes you more gay, but I don't think it makes us gay so much as make us more attracted to gay/bi men who actually validate our gender identities, whereas pre-transition, many of us avoided straight men who simply viewed us as female.

trans people going through HRT

Not op, but I went a bit through HRT, then desisted (primarily because of financial issues, then because I didn't identity with the opposite sex anymore). IMO transgenderism is understandable because many gender norms seem socially constructed, but transexualism (including HRT and surgeries) is a mental disorder or a maladaptive coping mechanism or immaturity leading to people not actually understanding and not accepting their bodies function, and I believe social contagion is true. It is pretty concerning minors are allowed to HRT since they bodies including their minds didn't fully develop yet (which goes until age ~24). There's a ton of detrans who regret going through transexual procedures.

I am transfem, and prior to transitioning I was bi. Since starting HRT, I tend to have an aversion to men sexually and am more lesbian aligned now.

I don't think this has anything to do with you going through HRT. It just shows how your natural hormones and nature are still strong enough to do what is natural. It's just immaturity; time went and you matured, even with HRT. Most natural women are actually attracted solely to men in comparison.