I had said this earlier as well. I think this is a weak sauce attack. It was reserved for Killer as well. Oda starts off with garbage attacks and works his way up with his character.
This occurs in reality as well. Fighters generally gauge the strength of their opponents by using common moves, testing strengths/weak points by sizing up their opponents. No one ever starts off with their Ace attack, they hold it to the end in the case where itβs usually self-harming, complicated, or not necessary for that fight. [Luffy not using G4, in FI, PH, Dressrosa all the way towards the end]
Given that Zoro used a basic Onigiri attack and cut Kaido, tells me so much is in store for Zoro.