This is someone from the trans community speaking. If you guys want to buy it, I won't stop you, but it isn't just a matter of people getting fussed over it for the sake of it. On one hand, I understand the hard work the game developers put into it, and maybe you have a nostalgia for the series.
But even if J.K. isn't involved in the game, she gets Royalties from it, and likely a decent bit. That's kind of what where a lot of people become uncomfortable. She very likely will be using some money to fund against the trans community and she's done a lot to dehumanize and attack the trans community. I've seen so much vile hatred towards the community, including a Twitter Account called "Valid Ls" which dedicates to making fun of and dehumanizing the trans community and has even lead DDOSSING on Discord servers ran by trans people. That makes me genuinely scared of ever coming out. Even if I may have a slightly more open family compared to others, I fear not "passing" to people and being subjected to harassment. I fear opening my mouth and speaking in a voice I HATE and outing myself when I am going in a career where the ability to speak is paramount. I fear professional backlash from a traditionally conservative profession. I fear laws like what is being passed in the United States attacking and dehumanizing trans people coming to my country. I'm scared, and the actions of people like J.K. Rowling have added to it. They're dangerous. So I can't, in good faith, give a single cent to this game if a sliver of it will go to a person who will continue to fuel an attack on not just me, but millions of people who aren't out to groom people, who aren't out to fucking rape women in a bathroom, but just are uncomfortable in their skin, feeling detached to what they were born as, wishing to live life where they can wear something that makes them happy, have their hair in a way they like it, and just feeling authentic. This soiled the memories plenty of former Harry Potter fans in the community has towards a series of books they likely read as a kid and have a strong connection to. If I buy this game, I feel as though I'm just legitimizing a person who has said horrible things and that she can just say whatever she wants and not face consequences about it.
So if you just love Harry Potter too much, love the genre of games, or buy the game, it's your choice. I hope if you get it, you have fun. But don't think that people are just freaking out because. In the end, sometimes, if you believe something, you should speak with your wallet. That's what I'll do.