First of all, there is no such thing as a yeastless crust. Yeast is all around us, it would be impossible to avoid getting some yeast in dough.
Now, it's possible that they switched from a leavened dough to an unleavened dough, but, looking at the pizzas, I find this highly unlikely. When they talk about going yeast free, I would bet any amount of money that they are merely just talking about the fact that they are no longer purchasing yeast. This means that they are either using the existing yeast in a piece of old dough for the next batch, or they are using a sourdough starter that they've cultivated and maintained. Since sourdough changes the nature of their pizza pretty dramatically, and could potentially negatively impact their extremely loyal customer base, my money is on old dough.
Old dough and commercial yeast are, from the sake of the end product, one in the same. Two different forms of the identical form of yeast.