The problem here is that you are assuming that the person’s identification with a particular gender is concurrent with the beginning of the public expression of that gender identity. Based on what I’ve heard, read, seen from my cisgender perch, that’s not how it works. It may be upon self-examination that the individual has attempted to express and identify with the target gender their entire life, but were quashed by parents, schools, etc.
So, you CANNOT say that the identification began at the time of public transition. Sorry, no sale.
University of Florida
But if people come out at a certain point, what else do we as catalogers have to go on? If we say Chastity became Chaz in 2008, we are not implying that the gender identification is irrevocable. We’re just saying that to the best of our knowledge (admittedly fallible), a certain gender identification started on a certain date.
Just some things to consider.