Norma, cheese melts/tastes differently when it gets heat only from above vs. heat from below AND above. It might seem like a piece of bread is a good substitute for a pizza skin for testing melted cheese, but it's really not. Cooked bread has most of the water driven off. Without the water, the bread becomes an excellent insulator, so the cheese is only getting heat from above. With raw dough, you have heat from below converting the water into steam, which, in turn rises, melting/bubbling the cheese from below. This is why parbaked crusts never melt the cheese well. It's also why reheated slices tend not to bubble the cheese any further.
Without the heat from below cheese doesn't bubble or cook all the way through. It doesn't give off all it's fat nor does all the flavor come out of it.
In other words, once you get this cheese on a pizza, it will taste very differently than your bread test.