JKR is actively politically involved in the persecution of trans people and the protection of transphobes. Even if she does not directly profit from an individual piece of HP media, the success of any HP media strengthens her brand and thus her political power.

That's why it matters. Not an abstract question of "death of the author" or the Ship of Theseus of adaptations of adaptations, but the single contemporary living human being who converts Harry Potter's cultural cachet into actualized hatred.