I really don't know, but do you think that Dragon maybe has ate a DF of wind? Or he just uses haki maybe... I don't think he has any power related to a dragon. I think his powers are limited to wind, in all his moment in anime or manga we always see the wind getting stronger... And I think he control the weather and that makes him capable of flying. I think he would beat the crap out of crocodile because if he has weather abilities, like making rain crocodile would be fuc***. But wich of the type of DF would it be?