I answered my own question here in a post below.

If I could delete my post here, I would. See my answer below for details if you're having trouble with the participants of a share not getting notified of an owner stopping it's sharing.

I just saw these questions just now. The forum bot didn't notify me these were here somehow. Answer in separate response below

Interesting sample. I'll have to do some experimentation with it. In one of his comments, he states the following: "The purge API posts an NSPersistentStoreRemoteChange notification after finishing its job, so observe the notification to update the UI if necessary." (line 104 of PersistenceController+Share.swift) But in my own experience, this was not true. That was the issue I was having that led me to the other solutions I came up with. Maybe they've changed things to fix that now, in which case my solution would no longer be necessary.