Got a reply to my report and according to Apple this is intended behavior. While the device shouldn't receive a push notification, CKSyncEngine will still deliver the changes on the next fetch.

Experiencing the same. This has been reported a couple times now: https://developer.apple.com/forums/thread/774014?answerId=883341022#883341022

Can confirm. This is fixed. Tested with Xcode 15.3 RC (xcrun version 68). It even shows an error message if the string couldn't be parsed.