I wouldn’t die on this hill!
It wasn’t pronouns, he was refusing to call her by her ‘new’ name in class, arguing it is compelled speech, which I just think is pretty rude. There is also something about a Maths competition which I can see both sides of. She asked if she could enter and he said ‘of course, you are a girl’ and entered her under her previous name. There are so many more diplomatic ways around this, such as saying your sex is female and it is open to all members of the female sex, however you know think of yourself, and use her new name.
If you are gender critical, surely that goes for names too? If Harriet wants to call herself Harrison, why would I care? He decided to gesture at her silently instead, which would be pretty offensive.
In the article I read, pronouns weren’t even mentioned.