One imagines in this case the current board discussed this in a non-board context, scheduled a meeting without inviting the chair, made quorum, and voted, then wrote the PR and let Sam, Greg, and HR know, then released the PR.
Which is pretty interesting in and of itself, maybe they were trying to sidestep roko or something
>>dekhn+(OP)
Not inviting the full board would likely be against the rules. Every company I've been part of has it in the bylaws that all members have to be invited. They don't all have to attend, but they all get invited.