I'm literally using the manga and how Oda describes Lunarian abilities. You're trying to interject YOUR headcanon about recovery or something.
Which was born from 1 panel of King having flames where he was cut and nothing else happened before or afterward.
"I've hit him with a few slashes, yet he's not bleeding!!" He's talking about generally, because we see he hasn't hit King with a few slashes all chapter, unless you count the one's King blocked. But Zoro probably isn't referring to those.