This demon is trying to trick you into spending twice as much on summoning salt because they have stock in the company!
Also it won't work and demons will eat your ass in a non-consensual way, salt is used as a symbol of purity and the additives/mixture by definition make it non-pure (salt).
No, the question really is whether potassium chloride by itself would work, also being pure (potassium) salt.
That's just propoganda by big demons. They want to you to buy salt so they can season you. Why do you think people say garlic will repel vampires. Sheple, all are sheple. That's just vampire propoganda.