Please tell me someone is picking this up on Twitter? I though identifying out of your race was a huge NO NO.
It sort of is and it sort of isn't. If you're a Good Person, then no-one can question you. If you're a Bad Person then you can be denounced for it.
Whether you're a Good Person or Bad Person is hard to determine, and this is an unstable equilibrium, as the act of "falsely" claiming an ethnic identity is Bad, but obviously a Good person wouldn't do that, so the question of whether a person can be flipped from Good to Bad by being called out, or whether such an accuser would be Bad is a complex social dynamics question.
You can certainly get away with it for some time. But when you lose it, you lose it hard. And sometimes that's hilarious, as in the case of some poet(?) in Canada who was falsely claiming to be Native Canadian, and eventually got called on it, by a load of people continuing to very studiously ignore that he was also a man claiming to be a woman.
During Maya Forstater's first hearing, someone from CPD's HR (American) did talk about how they were totally self-ID.