Thanks @Luka, this info is really helpful. My thinking was that GuestOS images contain the state and logic of the protocol, but of course there’s also the API for interacting with the registry etc. which may have changed between versions. Now I understand why there can of course be breaking changes between versions (unless the +1/-1 version steps are adhered to). Makes sense. Thanks again!
I’m intending on rejecting this proposal and the other similar one, given that neither of them adhere to this rule. They both skip Release: 94fd38099f0e63950eb5d5673b7b9d23780ace2d - ICP Dashboard (internetcomputer.org), due to the unassigned nodes being on: