Were I understand, that the information is existing in the relation, doesn’t that also apply to admin_level, and actually even more, as one way can be a boundary of several admin_levels. Shouldn’t admin_level be removed as well?
I am trying to think of a rhyme or reason I would have done it that way and am drawing a total blank. As you noted, once the tag is pulled into the relation you should be good to clean up the ways. Must have just been a late night editing oversight on my part.