The part about Zoro’s “upper limit” is just some fanboy reasoning to try and overrate him, as if we’ve needed to see it to know exactly where he is. He struggled against Hawkins and Killer and Gyukimaru in this arc alone, but we need to see his “upper limit” to tell exactly where he is, like we couldn’t ever tell. Zoro would have gotten destroyed on Dressrosa had he fought Doflamingo. He’s a good distance behind Luffy which means he’s a sizable distance between Law and Kid. So no, we don’t need to see his “upper limit” and we Oda wouldn’t need an excuse like that because it doesn’t matter.