People with these DSDs do not fit a male or female classification because they have a mix of sex traits from the two normal development pathways, so it's meaningless to talk of their birth registration as 'wrong'. Unlike anyone else (including trans people) they can (but not must) change their registration with retroactive effect, depending on their treatment choices. Their registered sex is their biological sex, and the case law clearly distinguishes between the April Ashley situation (sex = gonads + genitals at birth, personal feelings irrelevant) and the W v W situation (sex assigned pragmatically taking into account full picture of birth traits, treatment choices, and individual preference aka gender identity).
This person's employers could always have excluded her because she looks like a man, but not because she is one, because she isn't. FWS did not change her legal situation, but would have done if she was a transwoman. Her manager did not realise this.
I'm not endorsing the case law, just describing it, but I think it works well, just isn't very intuitive.
In a sane world where transwomen are not allowed in the ladies, anyone encountering this individual in there could be tolerably certain that she is a woman with a DSD. But if any doubts remain, they could still ask her to leave.