But how do you explain Oden and Law's reactions?
It could be two things imo.
Either
1.Oden and Law do not have barrier haki, thus when they are witnessing such powerful attacks done from a distance they are in awe.
Even if Oden and Law have seen barrier haki, the application of CoC takes it to a whole other level as an offensive tool, so they can simply be shocked how an attack done without contact can be as effective as they are witnessing (this might be a bit of a reach though).
Tldr;
Their reactions are to highlight overall haki mastery/proficiency (application of high level CoA and high level CoC) vs simply advCoC or simply barrier haki.
Which
does make (some) sense.
OR
2. AdvCoC is just a copy of CoA where it has levels/versions to it and non contact is the lvl 2 version of CoC regardless of any CoA application.
My issue with number 2 is the emphasis Luffy puts on learning non contact from hyou in prison. Which is a CoA application.
The counter argument would be learning how CoA flow works helped Luffy apply the same logic to CoC, but that requires more assumptions (and it strips CoA of it's use completely, or uniqueness) so I don't subscribe to it.
Anyways thanks Oda 👍