a trans woman is and has always been completely a woman from the moment of conception, and her life as a boy was due to parental error (ditto for men and non-binaries). Failure to completely alieve that is a faulty intuition on your part.
This seems to me like an empirical question open to serious doubt. I certainly agree that people should be referred to by their preferred pronouns, that failing to do so is considered extremely rude, and that this social norm still seems like a good idea after thinking about it carefully, such that we shouldn't hesitate to shame people who willfully violate it. But to insist on editing our descriptions of the past in order to fit the categories people belong to now just seems inaccurate, unless it's actually the case that gender identity is innate and immutable in almost all instances, and I just don't think that's true.
For example, I don't think we actually know what the demand curve for sex changes looks like: there are at least some people who frequently or occasionally fantasize about being the other sex, or non-binary, but don't want it desperately enough to actually do anything about it given the constraints of currently existing medical technology and social norms, but who might consider doing something were those constraints to change. (Just---don't ask me how I know this, and I won't tell you.) Telling a closeted transvestite that he's actually in fact been a woman this entire time by virtue of what he'd like to be in a glorious transhumanist possible future just seems untrue, for the same reason it seems untrue to say that an accomplished physicist was always a physicist, even before they learned how to read.
We have some idea, actually, insofar as the number of trans people who get GRS is much smaller than the number of total trans people (the procedures are quite costly, often not covered or completely covered by health care providers, seldom available without travelling long distances and rarely performed on patients less than 18 years of age, or with certain medical contraindications). The number of people who've actually had SRS serves as a very crude lower limit against which you can check other numbers and get some idea of prevalence.
If it's worth saying, but not worth its own post, even in Discussion, it goes here.