Mac to iPhone Messages Sync in iCloud

I'm having issues with the new iCloud functionality that syncs Messages between my Macbook and my iPhone. Both devices are on the latest operating system (High Sierra 10.13.6 and iOS 11.4.1). When I delete a message on my Macbook, it does NOT delete it on the iPhone. Yet, if I delete it on my iPhone, it DOES delete it also on my Macbook. I've gone through the setup on both devices and, since it syncs in one direction, it should also in the other. Is anyone else having issues with this? Is it a bug?