Kaido and BM didn't show internal destruction either but that doesn't mean his CoA potency is above them lol. Internal Destruction is an advance application of it, but it doesn't make your general CoA potency better lol. Zoro's CoA potency feats vs Kaido are above Luffy's general CoA feats. As for barrier, Zoro showed it, too. His feats of CoA against Kaido + the hakai feat is head and shoulder above Luffy's feats while using same variation of CoA. Sure, he has internal destruction, and that's advance stuff, but it doesn't translate into CoA potency. Zoro's CoA can still be more potent without ID.
Luffy was huffing and puffing in 10 minutes into fight vs Katakuri, too. Characters huff and puff all the time lol. It doesn't mean Luffy's more enduring- Thriller Bark proved that Zoro's pain tolerance and endurance is far more monstrous than King stuff.
No scabbards outside of Sulong Neko, Inu and the combined Togen Totsuka (which had Sulong Inu) managed to cut Kaido's dragon scales, no?