This page of Documentation should have a warning saying that a physical device is required to test the automatic syncing of NSPersistentCloudKitContainer
On the page, Mirroring a Core Data Store with CloudKit I can read in the section “Set Up Your Development Environment” A sentence reads “You can run and test Core Data with CloudKit apps using Simulator. You may also test with multiple physical devices logged into the same iCloud account on a good wireless internet connection.” But no explicit warning that the simulator will not have the same experience as a physical device because it does not receive push notifications.
On this page, Synchronizing a Local Store to the Cloud in the Section “Configure the Sample Code Project” a note about using physical devices should be included to see the automatic “live” syncing using push notifications
I can’t wait to use this feature in iOS 13. Its a great addition to the frameworks and removes a lot of friction of working with CloudKit and CoreData