Sounds like they got scared by the bad publicity, then dumped it.
The hilarious thing is the allegations ride on the back of how ultimately poor the prose is. Which you'd think a publisher, gatekeeper, would notice.
I believe Ballard used AI too, but Hachette's actions are so clearly based on public opinion panic that they deserve the lawsuit. It passed their own vetting process. They needed random internet personalities, and eventually a Times article, to tell them it's bad / AI writing? They have one job for crying out loud.
There may be a way to prove she used AI for that particular story, via discovery, but I doubt it.