I actually don’t know exactly how it works (I’m sure nostr:npub1n0sturny6w9zn2wwexju3m6asu7zh7jnv2jt2kx6tlmfhs7thq0qnflahe can fill us in) but it seems like Nostur keeps a local copy of your kind 3 and then when you start it up, if it detects a new version, it asks you if you want to accept the changes or restore your old list. Very useful.