I'm on iOS 11.4 beta and macOS 10.13.5 (previously) and 10.13.6 now and having problems with Messages in iCloud on my Mac.
If I read or delete a message on my phone, it correctly is reflected on my Mac.
If i read a message on m Mac, it correctly reflects that on my Phone. However, if I delete on my Mac, it never warns me about deleting from Cloud, and that deletion never gets made on my Phone.
I've filed bug reports but wondering if anyone has encountered or has a suggestion.