Thats just one example. There are many others but I feel like if the point isn’t made it never will be.
She makes a number of claims about transitioning and detransitioning that are straight up lies, tries to conflate trans women with predators that must be denied entry to womens’ bathrooms, claims that the change in societal views toward trans issues threatens to erase women etc.
The reality is that JKR seems to have never dealt with the trauma of her rape and abuse so she denigrates trans women as being little more than predatory men in skirts. Thats why she brings that up in her post. She’s explaining why she is so concerned with trans issues and those reasons go back to that trauma never being processed in a healthier way.