I wonder if you did not know about that, or if you think that that person should share dressing room and showers with biological women.
If you didn't know about that, maybe now it's simpler for you to at least a bit see how JKR is thinking?
https://www.theguardian.com/uk-news/2023/feb/28/trans-woman-...
(Just to avoid misunderstandings: Such events are of course very rare, the trans people I know are kind and lovely people)