Apple, the Cupertino tech giant had recently released the iOS 11.4 update for its devices. The new update brings Airplay 2 and Messages in iCloud to the iOS platform. Both the features that are rolled out with the latest update were much awaited and the users have waited almost over a year to get the features. However, it seems that the 'Messages on iCloud' are not functional as it was intended to be.
The Messages in cloud feature allows a user to sync their iMessages (including the SMS) across their entire Apple device range no matter if it is an iPhone, iPad or Mac. The major benefit of the Messages on iCloud is that when a user deletes a message from one device then it will vanish from other devices in the Apple's ecosystem. A user will no longer need to delete the iMessage chat history on every device individually. However, this is not the case at the moment.
At present, Apple has released the 'Messages in iCloud' feature only to its iOS 11 devices. So, if a user now deletes a message from his/her iPhone the message will no longer be available on the other iPhone or iPads, however, it will still be available in the users Mac computer.
As strange it might sound, the feature is yet to be made functional for the Mac devices. The reason behind this is that the Apple devices need to be running the latest software in order to access the 'Messages in iCloud' feature. We all know that the iOS 11.4 update was rolled out for the Apple devices yesterday. The update is available for iPhones/iPads, however, Apple is still to release the macOS (v 10.13.15) update. This is the reason why the new feature is not yet active and is missing from the Messages settings on Macbook.
Also, as per GadgetHacks, the macOS 10.13.15 is in beta phase presently and is expected o be rolled out to the users over the course of next few days. The update will also bring the 'Messages in iCloud' for the Mac devices, which will make the sync feature to work as intended. This will reduce the need for maintaining iMessage chat history.