Except Zoro didn't awaken CoC at the beginning of the series and took as long as he did to master it. He mastered the ability in a matter of minutes while Luffy went through 2 years of rigorous training to control the same ability. If it's about Zoro taking this long to awaken the ability, then yeah, it's perfectly logical to say he took this many chapters to awaken the ability. That, however, doesn't change the fact that the guy skipped all classes and still performed as well as the top guys in the class, if not better.