You are conflating gender identity with sexual orientation. A woman attracted to a man is heterosexual, trans or not. But in either case this post has absolutely nothing to do with sexual orientation.
I'll speak personally for a moment. Note this is my experience and not universal by any means. Having a penis absolutely disgusted me. It is not that way for all trans women, but for me it was revolting. I hated seeing it, I hated interacting with it, and I couldn't stand anyone else to interact with it either. It made me feel gross, like I had some kind of growth on my body that was entirely foreign to me. I was deeply ashamed of having one, and several times in my own childhood, long before I knew what sex was at all, I had recurring strong feelings about removing it.
My first sexual experiences made me sick. Simply sitting there and being able to feel it, knowing it was there, made me feel sick. It was wrong, innately wrong that was not how my body should be. For years and years while my friends and peers were maturing and experiencing sexuality and romance I was incapable of enjoying those things. I had sex, and I dated both straight women and gay men. I never once felt like my partners truly understood me, and all the time felt that I was lying to them and that they really didn't know who they were dating. Being seen and treated as man, even in queen context, made me severely depressed. And when it came to sex I was a passive participant in most of it. I felt no enjoyment with gay men or straight women, and would lie a lot about whether I was actually into what was happening. Feelings of shame and guilt would consume me for days after. Feelings of disgust at my own body, revulsion at the things people did to my body, and dread at the way my partners saw me.
This has entirely changed since I've had bottom surgery. I transitioned over 8 years ago but only recently have been able to get vaginoplasty and it has totally revitalized nearly every aspect of my life. My body feels like my own, and my partner has never known me as a anything other than the woman I am. They recognize me, they treat me very well and validate me and my feelings. Sex never makes me feel ashamed, having sex is enjoyable now. Just existing at all is free from the constant dread of knowing my penis was there that it existed at all. I feel whole in a way I never have before.
I transitioned for me. Not for anyone else. I got vaginoplasty for me. I didn't do it to fuck men, or to fuck women. I didn't do it for purely sexual reasons. I did it because having a vagina has made me infinitely happier. Because I deserve to live in a body that I love, a body that makes me feel beautiful and happy not repulsed and ashamed. I transitioned because this is me, this is who I am. I'm not a man and I never was. And now I will never have to pretend to be ever again.