I disagree😓. For your logic to work you have to assume that Enma is at the top of its grade thus it’s ascension in rank when it becomes a black blade as if that weren’t the case, Enma would remain its in current class & just be better than the rest. Also if any of Zoro’s other swords become black, we’d have to assume they were always top of their rank thus the ascension in rank. So imo its simpler to just assume a blade goes up in rank when it becomes black. As such, Yoru should to, if it was indeed originally a supreme blade as becoming a black blade makes it incomparable to any blade in its class.