Did you stop to think that BB can't nullify Kaidou's flaming torch? Because he simply finds himself in the center of it while coated in special flames and Haki.
So that BB can nullify Kaidou's attack, he first needs to go through these layers until he reaches his main body, the Logias are easier after all, if they expand their bodies, BB just touches them and that's it, like Smoker in Punk Hazard, Luffy's case here he needs to use Haki to make BB stay away.