roshvrishon -“He was a talmid chochom and he baked the pizza, he insisted it was a regular piece of bread and couldn’t understand why no body was washing on it. He felt that the topping was superficial and didn’t affect the dough itself.”
Perhaps he was Talmid Chochom but didn’t know S’A. The Mecaber says Simon 168 #7 there are different ways to make a Mezonos. The second way is a Machlokes between the Mechaber & Rema on how much other stuff. But on the First way there is no Machlokes. This case is similar to Pizza. It doesn’t have to have more other stuff than the bread.