Some good points. I think the problem is that there are (at least) two things going on when it comes to dating someone who is trans. It can be looked at on a micro level — what happens (or doesn’t happen) between two people — and on a macro level — what that means generally. You are right that there are a lot of unexplainable things going on when it comes to dating, and you can’t put attraction, or lack thereof, down to any one thing. On the other hand, having a hard ad fast rule about a certain group of people (e.g. pre-op or non-op trans people) does send a larger message. It is also a matter of perspective. To a trans person, rejection can be invalidating. If someone is generally attracted to men, but not a trans man, that can be invalidating to the trans man who just asked you out and got shot down. In their eyes, it is an invalidation of their gender — by being born with a vagina they are somehow not “man enough” for you. That’s probably not how you think of it, but that can be how it looks.
It also is unhealthy to generalize. Two of my best friends are a couple in which one is a cis lesbian and the other a trans woman. When they first became friends, to test the waters, the trans woman asked the cis woman if she would ever consider dating a trans woman. The cis woman said, “hell no!” She didn’t realize that the trans woman meant herself. a few months later, they started dating, then moved in together. That was about 9 years ago and they are still doing great. They have one of the best relationships I have ever known. So, I don’t know that anyone can ever safely generalize.