Because Via 313 operates with limited space, I believe they decided to go with a Bakers Pride countertop oven. I don't know the exact model and age of the Bakers Pride oven that Via 313 is using, but it may be something along the lines of the models shown and described at http://www.bakerspride.com/specs/Hearthbake/HB_P44S_P44BL.pdf
and at http://www.bakerspride.com/specs/Hearthbake/HB_DP2_DP2BL.pdf
. The latter document goes so far as to say that the Model DP-2 is "Perfect for pan pizza". But, either way, the oven will dictate the temperatures and bake times. On the matter of the pizza stones, my understanding has always been that Bakers Pride uses ceramic stones for its ovens. In the case of the countertop units, the specs say that the stones are ceramic. In the case of the regular Bakers Pride deck ovens, the specs specifically mention that the stones are Cordierite. There will also be a difference in the thickness of the stones, as you noted. In the case of the countertop units, the stone thickness is 1/2". For the regular Bakers Pride deck ovens, the stones are 1 1/2". As you correctly noted, these differences will also dictate bake times.
As for the application of the pizza sauce after baking, it is possible that the low ceiling of the Bakers Pride countertop oven that Via 313 is using, along with a small cavity, results in overheating and excessive drying out of the sauce at a temperature of 525 degrees F for 15 minutes. Since the pizza is hot when it comes out of the oven, there should be no problem adding the sauce at that time. That will even retain the nice freshness of the tomatoes used in the sauce. When I was re-reading the Buddy's thread, I remember that steel_baker, who is no slouch at making Sicilian style pizzas, insisted that, in the case of the pizza that he had eaten at Buddy's, the cheese and the sauce were both added after the pizza had been baked, as is sometimes done with Sicilian style pizzas. However, there was no evidence of this and he later agreed. In Via 313's case, I think the oven may have been the reason for adding the sauce later.
On the matter of the two-cheese blend used by Via 313, I was reminded of the many types of cheese blends that I read about over at the Buddy's thread. The choices that our members talked about included mozzarella cheese (which I believe some of the Detroit-area pizza operators use), Parmesan cheese (which steel_baker insisted Buddy's was using around the edges of the pan), provolone (which, like mozzarella cheese, is a pasta filata
cheese that melts like mozzarella cheese), and cheddar cheese (mostly white cheddar cheese). Some of the members created actual blends but others kept them separate on the pizza, using one type of cheese for the center and another around the edges, as does Via 313.