i agree with you that "advanced" only indicates a higher degree of mastery over haki
the term advancement/advanced haki was taken to seriously by the community, it is indeed canon, but it's only said to describe growth and levels of mastery.
"advanced CoA" or "ryou" were created right after chapter 937, and it stayed that way for 10 chapters until chapter 947 where we finally learned that it's called "outward haki", by the time the community have already settled on "advanced".
the first one to say it was rayleigh, in a flashback during luffy vs katakuri fight:
the second time by luffy when describing the technique that rayleigh showed him,
in the unofficial scans:
the official translation:
however, i disagree with what you said about that you need to master ryou in order to infuse yourself with CoC:
-the ability to infuse yourself with CoC is rare even among CoC users, mastering ryou won't grant you the ability.
-ryou mastery is not necessary to infuse yourself with CoC (yamato can infuse her club with CoC even though she can't use ryou).
-ryou is just a complicated way of using haki, it means
infusing yourself with outward haki.
-basically. CoC has the same applications as CoA.
here's how i think the applications of CoA and CoC:
CoA:
INWARD:
1-invisible
2-hardening
OUTWARD/RYOU:
1-barrier
2-internal destruction
CoC:
SPIRIT OVERWHELMING (basic)
INWARD:
1-stronger hardening
OUTWARD/RYOU:
1-stronger and larger barrier
2-deeper internal destruction (i'm not sure about this)