well if you dont have any visual indicators
then theres no reason for anyone to think you have it
we dont need to see garp with it in that scene because we have seen him in prev ones. for aokiji we do and in that fight we didnt.
I don’t have the authority to affirm he used COC coating, I just believe he did.
We know that Aokiji channeled his haki off-screen like Garp since his fist is black when punching Garp
And both punches to te face are depicted with the same type of lightning that comes from each side.
Visually it looks like both used the same type of haki.
It’s more likely they both used COA or both used COC than Garp using COC and Aokiji COA based on this.
I’ll just say that if this is COA only, this is by a gigantic gap the most potent display of COA in the verse.
if Kizaru ends up using COC ( unlike Extravlad I’m not certain about it happening) then it makes sense Oda would keep it ambiguous as it that type of « reveal » would be more impactful in the main plot.