In biology there's this thing - genotype vs phenotype.
Easily adapted here:
Sex (genotype): this (medically certified)
Sex (phenotype): this (or that or that other one or undetermined or whatever - to each his own)
In this brave new world I'm sure someone will soon come up stating "I'm a 73%-27%" or "64%-36%" or "x% - (100-x)%" now that simply stating "non-binary" is already passé.
It's time for exact science.
...
Gah.