The name issue is really difficult. It sounds like he's not necessarily done a good job of cutting through this in the tribunal.. and could be harming his case as a result. I hope not.
To add a thought from my own perspective. My daughter began using a "neutral" name at school, in a limited and unofficial capacity, without us knowing. Eventually the school told us and we cautiously went along with it, saying yes (we didn't really have much choice, we felt that our hand had somewhat already been forced by the circumstances) to agreeing to it being her "known as" name. Meanwhile, I was busy learning all about this weird new world of gender identity (I had no idea about Mumsnet at this point), following her request for puberty blockers (which we said no to, following what we read on the NHS page about gender dysphoria) about 3 months prior.
As I continued to learn more, I was getting increasingly concerned about this name. Not the name itself but what it represented: an untethering of my daughter from the reality of who she is, a chance to be a blank canvas and reinvent herself in whatever she understood to be her "authentic self". When she told us at Christmas time that year, about 3 months after the new name started being used, that she was happy for us to use her normal name at home, I grabbed it with both hands. She's now her normal name at home and with family and friends, and her "neutral" other name at school and activities. Yes, it's a bit weird but I'm going to keep her as tethered to reality as I can, while she works through whatever is in her head about all of this.
It's possible that something similar to this was behind his concerns about the name e.g. if nobody else was going to help her keep a foot in reality, he would. Whether that's safeguarding or overreach, given he is a teacher not her parent, I'm not sure. But I can fully empathise with the place of concern that it is presumably coming from.