So instead of accepting the blatant answer that is right in front of your face that it wasn't used because it obviously can't work on poison, you're just gonna assume it can, and Oda just made it up on the spot?
It seems that you're just looking for a reason to complain.
Make sure you keep that same energy when Zoro survives double the pain of Hakai, and whatever injuries he receives from King later this arc. Don't want to see you running around here talking about how awesome Zoro is because he survived double the pain of Hakai, and a multitude of other injuries. Remember how it's going to be an asspull later down the line. :cheers: