I wonder if its less about habit forming as the article supposes, to lock consumers into shopping at one or the other, and more about confusing consumers. If both discount in an alternating fashion, consumers are not benefitting by going to one or the other regularly. They only benefit if they plan their spend across both but that becomes too time consuming. It might be more about keeping pricing much more fluid. If the price is always different, there is no usual price. Its hard to price compare and less likely for price rises to he noticed as consumers can’t possibly track all prices of all products.