You made this up and it happens to go against what we can understand. First of all there's no rule in place to say he must, second...why do you think little kids unconsciously use Haohshoku, but it's out of the question for a guy who managed to even learn the other, conscious forms of Haki without understanding it
Luffy, the CoC specialist, has the CoC control to selectively knockout characters, combat genius, with more understanding of ryuo than Zoro, who learned adv CoC from having it used against him twice, it was portrayed as an impressive feat and the culmination of knowledge, control and power.
Zoro just overclocks his haki out at full power through Enma, doesn't have the same weight or build up, and yes comes off as bs.
UNLOCKING
base CoC is just a matter of genes and sufficient blooming from stress, not training or understanding.
Hence why an untrained Luffy unlocks it pre-skip and why Doffy/Ace can unlock it as kids.