He actually doesn't grab him, he puts up his vortex. What he says next then can be interpreted two ways, the way you went or he could be saying "you can't make anymore quakes" meaning because he will absorb them all like he did that one. If you look at the pic though you can see Teach's left hand is behind and his right hand is using his DF power, he's not actually touching/holding WB.like I said, Haki wouldn't make him cough up blood when slammed into the ground. Haki was very clearly stated to not be able to nullify DF powers. The only way being slammed into the ground would cause Luffy to spit up blood with the usage of Haki is if you imbued the ground with Haki.
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Teach grabs WB and says he can't make more Quakes.
Nobody's saying anything about haki nullifying DF's I'm talking about Haki allowing people to bypass Luffy's rubber quality and inflict damage like Garp. Luffy would still bleed from a haki punch. If BB had haki on his hand pushing down on Luffy against the ground that would create pressure on him where he was pressed and could make him spit up blood. It's not an impossible reaction.