He also told Luffy the presence of 500 animals stronger than Luffy.
Does that mean he's a CoO master too?....
i believe he has mastered the essence of common CoO..
advanced would be FS, Scope and etc that come in the domain of AcoO
sanji has nearly mastered CoO i'd argue and was capable of dodging Katakuri..
and you'd except Reyleigh in his prime to have disgusting instincts as well.
so having AcoO or not doesn't really matter it just and extra perk that you attain depending on what type of fighter you are..
For luffy he was fighting against Katakuri with average observation... and had to attain the next level... and he still till now admits or alludes to that he hasn't really mastered his common CoO completely..