I've just read something from another lawyer who's as fanatical on this as Jolyon, and he's spluttering about how this is a political judgment, and the Supreme Court is lining up with Trump and Putin, and Britain has become a more dangerous place for the trans community, yada yada yada.
He's a smart chap with a good track record in his field, but I don't believe he's a specialist in equality law. So on this he's just opinionating in front of his similarly minded political associates.
But he's not saying it was never arguable. Which suggests to me that, for all his bluster, he knew the law was messy and it could go a number of ways. He's just not willing to openly say so.
And that also suggests to me that Jolyon is shamelessly bullshitting.