I remember this case - and how aspects of it made me feel uncomfortable.
I'll start by saying that I fully support Kevin Lister not having to use opposite-sex pronouns. I also fully support him trying to get the college to see sense that it's a safeguarding matter when a student wants to socially transition. It's unfortunate for him that a) the college didn't look at it through this lens and b) the risks about social transition weren't as clear in the KCSIE guidance as they are now (from memory, this happened during the time that the KCSIE had just 4 paragraphs on gender questioning children and simply pointed to the Cass Report as being a thing).
However, where I found it uncomfortable is the way he seemed to use the maths competition as a way to publicly (i.e. in front of the class) tell the student about eligibility owing to being female. If I've remembered that incorrectly and he had actually spoken to the student privately, I owe Kevin an apology. Either way, I think he could have saved himself a lot of trouble by using the student's preferred nickname.
I do hope he wins, because it's important that teachers know they can't be coerced into using the language of gender identity. I also think it would be warranted for him to get a telling off from the court that it ain't what you say, it's the way that you say it... where the way that he said it (the maths competition) was in front of the class. I agree with the Banarama point (that is often made on this board) on many occasions, but on this occasion it does sound like he handled it badly.
As for speaking about a child publicly, I'm not aware that he spoke about the child in an identifiable way. So I can't see how it would be a safeguarding issue when he simply speaks about his case.