Okay so I have some genetics training and am GC ish, though I could still be talking rubbish, but hear me out ...
I think I kind of see where Eddie might be coming from. I think he said years ago that he had always felt somewhere between a man and a woman (can't remember exact words he used). I think I also read an interview years ago with Richard O'Brien where he said similar.
I think I remember Eddie mentioning the genetics thing years ago too. My understanding was that he felt that there may be a genetic element to him feeling part-masculine and part-feminine. I wouldn't be surprised if he was right that there may be genetic elements to being a feminine man or a masculine woman, just as some think there may be a genetic element to being gay.
I also wouldn't be surprised if there were differences in brain imaging between men and women, and that (for example) there may be some differences between the brain of a feminine man and that of a masculine man (I believe the jury is still out on the brain scan thing and I'm aware there are studies suggesting this may not be true).
So I guess what I'm saying is, I could well believe there may be a genetic element to being gender non-conforming or to experiencing gender dysphoria.
What I don't agree with is that this means you ARE the opposite sex. And I guess to me, transitioning is something you may decide to do, rather than something you ARE, though it may be a more likely outcome for those experiencing severe gender dysphoria.
Just my two pence worth anyway.