This chapter is a clear « pass the torch to the younger generation » moment.
Koby is clearly dubbed as « Garp’s successor » therefore there should be no doubt that he has everything Garp has on a lower scale and will end up stronger than prime Garp.
So yeah he can use AdvCoC.
The issue is not that he can already used it but rather that Oda did not invest enough time in his character prior to this chapter to make this reveal fullfilling.