Jorge, I cant answer that. There are regulations that say that if an ingredient is harmless and is below a certain level, it does not need to be mentioned. Also, if they didn't add anything, if something was already there, then there is no problem.
But to add to this, all I can say is that salt cakes badly unless silicates and other ingredients such as rice powder (starch) are added. I remember as a child during WWII, this was not done and we had to keep breaking the salt up in our salt shakers to keep it pouring. In fact, the Morton label went to the little girl with umbrella when they started putting in the additives. They used to advertize that Morton salt would pour in a rainstorm. Their motto was "when it rains, it pours".
So, maybe it is not a lie, but rather a loophole? IDK.
I have analytical grade NaCl here. It is one big lump in the bottle and sitting next to it is a container of Morton salt (non-iodized) and it is just like fresh sea sand and says "nothing added". I get different results from 3 batches of salt. Rock salt, food salt (nothing added) and reagent grade.