I renamed the “drafts4” tag to “z - drafts4” so that it would sort to the bottom of the list.
I have confirmed that there are no longer any drafts tagged with “drafts4”.
(Note: using Drafts on iPad Pro (12.9-inch) (3rd generation) running iPadOS 15.3.)
Expected: “drafts4” would no longer appear in tag filter list.
Observed: “drafts4” still appears in tag filter list, as does “z - drafts4” (see screenshot).