Funny how Oda is having Luffy learn this before his inevitable fight with Shanks, the swordsman whose CoC is off the charts....
I believe Shanks can use CoC even better than this
Possibly bigger Range to match Mihawk's Huge Slashes
And he can use it continuously to create pressure & defense around him (Similar to when he met WB)
And i believe this pressure is so overwhelming it can slow Time (As hinted by the Games)
This is why i believe Zoro will master advanced Haki to be able to cut & hurt anyone too
But Luffy will have Shanks CoC level of mastery for EOS
It's also possible Luffy will indeed take the sword given to him at start of Wano
After all, a Sword is a Symbol of piracy & Luffy doesn't have to learn swordsmanship
He can just learn to hold it & use CoC through it