please re-read alans original post at the top, it is about exposing the features from:
https://snapcraft.io/docs/keeping-snaps-up-to-date
to desktop users, nothing more. fundamental changes in behaviour of snaps need to be discussed for snapd itself, not in a desktop integration thread. there are already existing threads (linked above from several posts) that discuss this.
this thread is not about permanently disabling updates but about refresh.timer, refresh.hold, refresh.metered and refresh.retain exposure via the UI plus desktop notification integration of snapd.
and again: regarding your “example” that snapd slows/stalls shutdown, pretty please file a bug or open a thread in the snapd category and provide the logs you get asked for, since it is a bug.
this is unexpected behaviour that needs to be fixed.