It can, if you set a disk as the hot spare for that pool.
But a disk can only be a hot spare in one pool, so to have a "global" hot spare it has to be done manually. That may be what that poster was doing.
But a disk can only be a hot spare in one pool, so to have a "global" hot spare it has to be done manually. That may be what that poster was doing.
It's these reasons that I've decided to just keep a couple of cold spares ready that I can swap in to my system as needed, although I do have access to the NAS at any time. If I was remote like GP, I might decide to use a hot spare.