Those work by having coupon discounts only discounting from full price - you’re not allowed to stack discounts. But pizza places discount their pizza pretty much always

I like the fact that in Australia we still have local non-chain pizza places (and fish and chip and burgers places) where they make family pizzas sized for a family (or for one young man) with our own standard toppings which I haven’t seen elsewhere, and they cost less than similar amounts of Domino’s