People think Oda gives characters PUs for the fun of it lol. Zoro didn’t need to unlock ACOC there, if it wasn’t warranted to beat his opponent. He could’ve had the momentum shift with CoC being fully unlocked and Zoro learning his weakness.
Did coc give him extra speed?
Had he used asura after he figured out king's weakness, he would have beaten king.
Zoro didn't even beat king btw. King threw away his invincibility advantage for no reason when he even knew zoro was on a fucking timer.
Zoro using asura has always been treated like a very demonic entity. So king would have did the same thing he did when zoro unlocked acoc. Throwing away his invincibility for no reason other than irrational fear. And the end result would have been the same.