JK Rowling actually said when giving her views of transpeople:
"I believe the majority of trans-identified people not only pose zero threat to others, but are vulnerable for all the reasons I’ve outlined. Trans people need and deserve protection. Like women, they’re most likely to be killed by sexual partners. Trans women who work in the sex industry, particularly trans women of colour, are at particular risk. [......] I feel nothing but empathy and solidarity with trans women who’ve been abused by men. So I want trans women to be safe."
It seems to me that Boswell could be accused of transphobia in this comment: "in light of J.K Rowling’s comments and viewpoints surrounding trans people. Her views on this issue do not align with our school policy and school beliefs" that indicates Boswell don't agree with JKR's assertion that the majority of transpeople pose no threat, are vulnerable and need and deserve protection.
Or am I missing something...