The issue, as I understood it in this case was that he wanted it kept quiet until GTA6 launches, because announcing it to the public also announces it to Sony, and they'll patch it; normally that's fine, everyone just doesn't update, but given GTA6 is apparently quite popular, my understanding is that he wanted to let everyone get that one last update that allows GTA6 to run before they're stuck on that version.
So normally if the community found this stuff I guess they’d work together to make a jailbreak. Maybe they already were working on that with bug X but hadn’t told anyone.
The JoeClaudeUser posts publicly “Hey everyone I found bug X over here! I’m awesome!”.
Now it can’t be used because Sony will fix it. If they had already been using it behind closed doors all that work is flushed.