I think the point ZM is making is that the judgement is not about whether or not Forstater's statement was factual. Instead it is confined to a narrow question: whether or not her beliefs were "not worthy of respect in a democratic society." The original judgement said that they were not; that judgement has now been overturned: but, as the judgement makes clear, that is very much more to do with the fact that "not worthy of respect in a democratic society" is the sort of label that should be confined to fascist views, or pro-slavery stuff, or advocating genocide, rather than debating the topic of gender in the abstract.
The judgement very explicitly distances itself from expressing any views on the substance of the "gender-critical [its term] beliefs"; very explicitly reaffirms that "misgendering" (if repeated and deliberate) is "subject to the prohibitions on discrimination and harassment" that exist in law e.g the Equality Act; and also reaffirms that, as a matter of law, the Gender Recognition Act still applies, so that in legal situations anybody refusing to acknowledge a person's gender as recorded on their birth certificate, before or after obtaining a change via a Gender Recognition Certificate, would be in breach of the law.
See below, in particular, from para. 4:
"[Our decision] does not mean, however, that those with gender-critical beliefs can
indiscriminately and gratuitously refer to trans persons in terms other than they would wish. Such conduct could, depending on the circumstances, amount to harassment of, or discrimination against, a trans person." (emphasis added).
https://assets.publishing.service.gov.uk/media/60c1cce1d3bf7f4bd9814e39/Maya_Forstater_v_CGD_Europe_and_others_UKEAT0105_20_JOJ.pdf