Let’s say you have a man who has no problem being identified as a man and he makes no qualm about it and even identifies himself this way. But if he wakes up one morning and decides he wants to be a woman, and he not only wants people to identify him as such (or trans woman) he also wants people to consider that in the past he was also a woman/trans woman at heart, then what we consider about who he was at the moment in time when he was biologically a man is that he was a woman/trans woman and not a woman at the same time and in the same relationship
As I've understood it, you are building your inquiry based on time, are you not?
I am inclined to believe and I dare cite that even by just everything I could not and could understand about Einstein's theory of general relativity, there is no inarguable scientific law that you can build this upon. This was succinctly mentioned by Sidis here:
what is known of quantum mechanics suggests than paradoxes and inconsistency may be fundamental parts of the world. Or in other words, inconsistencies can be true in and of themselves.
To me, that the very logical physical science makes ample room for a lot of things robs us of any chance to philosophically decide what or what does not make a woman. Enso stated that clearly here:
. Without this implicit nature of what makes a women a women (or a man a man) then we can’t really come to a conclusion using logic because a dualism (male/female) cannot be nondual and dual at the same time (male v female being male/female).
To simplify for my sake, what we know both of science and of ourselves is simply too little. The very recognition of the vast unknown makes an infinite number of truths possible, including simultaneously existing paradoxes, which directly debunks the law of non contradiction if used to argue the spatiotemporal aspects of womanhood or femininity or even the construct of our genitalia. If our very spatio-temporal existence is limitless in its possibilities, to be a man and only a man at a given time is then pure nonsense. If our thoughts manage to be simultaneous among our subconscious and consciousness, how then can we decidedly utter that it is nonsense to be anything in between including non-binary gender?
I interpret that your inquiry is less a philosophical exploration but more an attempt at making sense of pre-existing social constructs. It's complicated because these constructs have been built from a time of lesser understanding compared to what is understood today. While tradition and repetition renders them valuable by virtue of cultural acceptance, it is also apparent that it cannot be a singular construct. Even if all of our personal thoughts and feelings were set aside respectively and if womanhood is interpreted just as a choice or even just as potential biological turnouts, the resulting probabilities are still more than just his and hers. The breadth of the factors that connive to result to our being is wide such that it even mathematically, we cannot just be a result of being an x or xy chromosome at the onset of our existence. Thus, the social construct must be decidedly archaic and equally alienating although still, evidently organized and by that makes it beneficial in some regards.
@John K succinctly and compassionately stated this:
I can understand why people have problems with the softening of the edges of gender identity though. There are social consequences beyond the individuals who wish to change their identification that need working through
In total, I think that we could simply accept that the paths of one are not the paths of all. Social constructs can still exist if it so wishes to for practical purposes, but it must not alienate. If science and math could argue that we are limitless, why then should we be limited just because of what is accepted by the majority?
If even the laws of humans are subject to revision, why not our minds and our interpretations and acceptance of what gives the other their claim -no matter how temporary- to being a soulful human?