I hear time and time again that if someone takes hormones, cuts their genitals and attaches a neovagina or neopenis to themselves, that's a "sex change", and they somehow change from male to female, or female to male.

Would that really be sex change though? If sex change is impossible, can you explain why it is, even if the sex organs are removed and neopenis or neovagina are present?

Have biologists explained why sex change is impossible? Any articles, blogs, tweets, or really, anything I can read on the subject?

Also a question about the definitions of male or female. Since the definitions are on the basis of development, what do you think of this comment that finds issues within that definition: https://imgur.com/I1sgKTY

So, what determines your sex is: if you have ovaries you're female, testes you're male, but on rare occasions there is ambiguity about whether you're male or female, e.g. maybe you have ovotestes. Do people ever e.g. have one ovary and one testis?

Anyway, let's consider the case of those trans women who undergo a full medical transition using this criterion. They no longer have their testes.

Does this mean they are no longer male? Note that if we did say they are no longer male, we still cannot claim they're female under this criterion because they haven't acquired ovaries, so what sex are they in this case? Are we to say the have no sex?

However, I think we can say they are still male because they were born male and developed the way they did because they're male and removal of the testes does not undo that. All the surgery and hormone therapy is achieving is to make the male externally resemble a female. What makes you male or female is thus down to whether you develop testes or ovaries in the first place, not what might happen to your body via surgery or unfortunate accident or illness subsequently. Would you agree?

This does then raise the question: Suppose medical technology was such that we could give trans women functional ovaries and wombs, etc in future. Would we regard that as a genuine change of sex, despite the prior male developmental history?

If the definitions take into account developmental pathways only, and not necessarily whether or not one has sex organs or gametes at certain moments, would it mean if technology were "advanced" enough to give the so-called "trans" functional sex organs of their opposite sex, for instance, functional ovaries, uterus, etc to a male, would that count as a sex change? Would it be correct to say the male became a female despite the body having developed as male?