Hmmm. On the one hand if we're doing a paxos-only catchup then we do want to keep this up to date. On the other hand, when doing syncs we haven't actually *committed* these because we haven't done the update_from_paxos bits, and aren't going to do so until we finish the sync. Especially with the mixing of paxos-only and full syncs I'm concerned this will lead to holes in terms of who syncs from whom, and what updates get applied or not.
Maybe it's all dealt with safely and easily, but I think this is butting up on some edge cases that we'll need to be careful about dealing with or (preferably) not having.