I checked 500's page on AG periodically to see whether the case has been made available for public or not. I believe it's still under review by AG's mediator, deeming whether the situation fit for mediation or not. I think, the way it works, once they deemed a situation fit to be called as a dispute, they reached casinos' representative and simultaneously made the thread public.
[Sorry for being a bit OOT]
Actually, no, I don't think they're much different. CG also share similar SOP where they will review the basis and nature of a case, deemed whether it fit to be mediated by their team or not, and would made the thread public only after those preliminaries. I think there were situation where cases were being rejected behind the screen due to its nature not fitting their criteria.
I think, on most situation, the thread was made public with the player's complaint as opening statement also already available for public eyes. On cases where it's still private, I think that's because they're reviewing the deeper elements of the case, the proof that the complainant submitted, while they've deemed the case fit and accepted to mediate.