For Enma
in Ryumas case we know that haki or propostions remain like his black was permanent black so using haki on a sword for years leaves a mark on the sword it seems like Odens haki made enma stronger and since Enma is special it prob contains odens haki permantly when Zoro fused it with his haki it unleashed the swords secret aura
Well none of this is true. We don’t know how black blades are formed and Oda will in fact tell us how they are formed. He won’t leave it to your imagination.
secondly Kaido said he could feel Oden in the scabbards as well yet clearly they don’t have Oden’s actual haki in them so where are you getting this shit that Kaido saying that means Enma has oden’s haki too
in fact We literally see a panel of Oden teaching the scabbards Ryuo and that’s what Kaido was sensing. They were imitating his haki technique