So it looks like it was indeed simply just the most asinine "down for maintenance" notice possible.
They should look into the possibility of just going read-only during backups like TTH does, even if that takes the form of kicking over to a read-only slave server ( which would be somewhat trivial to implement, even on a relatively weak server).
They should look into the possibility of just going read-only during backups like TTH does, even if that takes the form of kicking over to a read-only slave server ( which would be somewhat trivial to implement, even on a relatively weak server).