Not sure if this has already been raised, but isn't the real issue here that the SCJ copped out and singularly failed to grasp the nettle in the FWS judgment?
Although it would strictly have been obiter because the issue wasn't in front of them, they could easily have said that references to "men" and "women" in the Workplace Regulations should also be construed to refer to biological sex just as in the Equality Act. But they chose not to do that.
Yes, I know that back in 1992 the words "men" and "women" only had one possible significance (ie a reference to biological sex), but the SCJ explicitly did not do so when they probably should have done.
I'm not surprised an ET judge is reluctant to step where the SCJ apparently feared to tread[See note]
Apart from that the rest of the judgment (only Sandie complained, comparison of the credibility of the witnesses, the second respondent's appearance etc etc) is rubbish
[Note - Of course the SCJ may have belived this mess is not for them to sort out, but for the legislature...]