Will it eventually be removed from the MSE tag system? I wanted to ask the question a few days after the migration, but tried to give it some time to see if the more frequent automatic tag clean-up process did anything. I assume that process has now happened once or twice since migration, but perhaps not.
The odd thing is that if you hover over the tag on that newly created tag list, it still shows one question (the migrated one), even though that question lives on another site now.
Sidenote: I'm very hesitant to tag this post as a bug, but I have a hard time believing this is desirable behavior for tags. So, I'll go with "support" for now.