That's not how applied math works. Sure, two variables may cancel out when set to specific values and multiplied or divided together... however that certainly does not mean that the variables are meaningless in the overall equation!
My theory is the tariffs have simply been set by relative trade deficit and after Trump has announced them and been ridiculed someone tasked economists with finding an explanation for the rates. This formula kind of just works out if you estimate the elasticities for all import from all countries conveniently at 2.