I suppose its no bad thing for people to have a think about why single-sex spaces are so desirable that the Act makes a special exception for them, and other legislation mandates them in some environments. The reasons are obviously biological in origin.
But Phillipson seems to be limbering up to parse these reasons so that men can be excluded from these spaces but not those, on some kind of sliding scale.
And that is not what FWS says. The whole point of the ruling is that the Act only makes sense if you apply a binary test:
The reasons are good - no men allowed.
The reasons are bad - all men allowed.
None of this requires us, or their Lordships, or Phillipson to parse what the reasons actually are.
(Of course we do need to keep going on about the reasons, because at this rate every space that legally can be, will be made mixed-sex, in a colossal act of anti-women spite by the politicial class.)