What does that re-keying process do exactly? Surely it’s not just updating the key on the device itself, because then it wouldn’t do anything to stop people cla

What does that re-keying process do exactly? Surely it’s not just updating the key on the device itself, because then it wouldn’t do anything to stop people claiming encountered notes at the point of expiration, if I’m understanding this correctly. But it can’t be moving the funds to a new wallet either, because you don’t have control of the second private key yet. So… what exactly happens there?