I think thread OP is correct.
Toni wouldn't hack all these changes, being old school. The GB are supposed to accept the results of a 2/3 vote, I believe? I agree he probably resigned, rather than co-sign the recent changes.
I actually wouldn't be surprised if he'd handed in a DA letter. That would explain why he's stopped attending meetings (although I suppose it's possible he could attend via zoom without the publishers necessarily being aware? If they kept him off camera/anonymous for privacy).