Still key related. In order to get or replace a key you need to be signed in. Sign out afterward
You don't need to do that now. You won't need to ever do that in the future.... Downloading diagnostics and then uploading them to the forum / reddit / discord etc has nothing to do with the UPC, nor will it ever will
Fair point. Except to say that while they have your email address via registering the key, they also have absolutely no clue as to what version of the OS you're running. The same key file works for all versions of the OS past, present and future. IF you want to receive those types of notifications (if they ever send one), then it only makes sense that you'd be logged in so that the system would be able to discern if it's even applicable to you. Note that the vast majority of notifications are sent by your server itself relating to its own health and once again have absolutely nothing to do with the UPC
You're misinterpreting the statement. It means YOUR signed-in servers. You do not see, nor will you ever see any one else's servers and they do not see yours.