A census taker would decide what race you are, from categories thought up by other people.
https://www.census.gov/data-tools/demo/race/MREAD_1790_2010....
> While people nowadays are enumerated by race based on self-identification, until 1950 their race on the census was mainly determined by their census enumerator.[170] During this time multiracial people who were White and of another race were usually marked down as belonging to the other race due to the One drop rule.[170] The instructions provided to enumerators endorsed this practice.
It appears in this case the census is content in counting people who prefer a particular prefix and only counting that (which can be self-identified) achieves its aims.
Tbh I don't massively see how this changes how one might treat census data (especially since the numbers remain small enough). I would suggest that if your research requires data points for people born as women then maybe you should be looking for other datasets such as births.