I read somewhere that this could be their way of "testing" imessage in the cloud that originally supposed to come with iOS 11. The fact we all started seeing this with 11.2 is not a coincidence. My guess is they are testing the syncing to the cloud and using us all as guinea pigs before its released. Which is why so many of us with multiple devices (Mac, iPad, iPhone) show erratic behavior. I'd be curious on how many people that ONLY have an iPhone are seeing this.
This was raised in another thread and this happens irrespective of the number of devices and whether or not they are linked / synced.