Nah, the only narrative reason this panel exists is to tell us Zoro can damage King in his flame on mode:
It's possible that this got retconned too, just like Zoro initially making King bleed without KoH was retconned.
By the way, if King turns out to be truly invincible in flame on mode, he's at least jumping to low top tier territory, and would be stronger than Zoro. This would mean the fight was just PIS nonsense, cause Zoro had zero chance to win.