User blog comment:Xhatefate/DxD Updates~/@comment-73.46.6.122-20160620201135/@comment-24.113.252.213-20160621185350

"Wouln't it be Ddraig for boobs and Albion for butts instead?"

Remember, the Biblical God hates dragons, so he most likely wanted to torture them by sticking them with possessors who had their opposite fetish.

Hence:

Ddraig who likes butts -- Gets stuck with Issei who loves boobs.

Albion who likes boobs -- Gets stuck with Vali who loves butts.

You could say the Biblical God did this hoping that what happened to the Heavenly Dragons today (being called the Breast Dragon Emperor and Butt Dragon Emperor) would actually happen. Kinda like him saying, "If you love boobs/butts so much, then you should be called such."

This was just my speculation on the topic. Ishibumi has already dicked with these legendary dragons enough, I guess it's better he didn't go with this.