My main point is that AdCoC was mostly only used on the moment of impact when Garp and Aokiji connected, thus creating some sort of explosion.. It's a new application of AdCoC, short range strike.. And the reason of the training..
Perhaps, it might even be a Condensed version of Galaxy Impact, CoA level 3 + CoC level 2..
It's a point blank shot like CoA level 2 emission but an advanced Haki technique..