Are tags supposed to sync via iCloud? Or are they per device? I only have 5 out of 15 of my tags on one device. My drafts are all syncing as expected. I’m not sure whether this is an issue or by design.
Alternatively, the tags are syncing, but the interface is not displaying them or scrolling?
What, perhaps, you might be seeing is the recently used tag suggestion list that appears when you enter the tag field does not sync - which is intentional, as often different tags are more commonly used on different devices. As soon as you start to type a tag, the suggestions become a query and will include any matching tag.