That sub doesn't understand that its trans rights that they demanded have caused their problem.
Not only is a GRC only based on a diagnosis, the certificate itself is reasonably private. Therefore, for the service provider and service user, there is no difference to Fred before and after transition. Also Fred is indistinguishable from 'middle age cis man' Fred, and PC of GR Fred.
SSE are justified on the bases of sex, and designed to accommodate only one sex. Nobody can change sex, but if it could be demonstrated that a 'meaningful ' transition has taken place, that both service providers and users could live with, there's a good chance the courts would accommodate them somehow.
But reddit trans want to be women because they said so and to be in women's spaces.
Some now think its easier to move towards 'nothing without us'. If they cant use women's SSE, then they shouldnt exist.