This was my suspicion too. Their page and Amazon (illegally) suggest salt is the only ingredient, but the Walmart listing show it contains Sodium ferrocyanide.

My own safety concerns aside (this stuff literally degrades into (a small, but not insignificant amount of) deadly hydrogen cyanide gas in your stomach), it is made purely of mined and petro-derived chemicals. No organic production method is used these days.

So aye, it seems the ‘non-GMO’ is in fact meaningless in this case.