User blog comment:B214/Volume 22 spoilers/@comment-78.8.41.88-20161017150638/@comment-1359322-20161018162316

As seen in V12, Issei can't use CCQ without his Pawn Pieces, how can CCQ be considered Ddraig's full potential when it can't be used without the EP?

I personally view the CCQ & EJOD as similar thing. Issei and Vali used their own method to utilize the powers of the Heavenly Dragon. Whether or not it is equal to the Heavenly Dragon full potential is another issue. Issei isn't Ddraig, Ddraig's best may not be Issei's best vice versa.