Why would Garp restrict himself in a brawl, when he already attacked Aokiji with CoC?
And which CoA user in the series except for fucking Oars would need battleships for sandbags?
Luffy was training ID CoA blasts on trees.
Honestly seems much more likely that Aokiji uses CoC this chapter. And it's not like it's illogical for any admiral to have it- they have fucking top tier ambition afterall