I then turn the oven flame off completely for several minutes. The temp equalizes across the bottom stone, let's say 700 degrees.
Nice pie. One can't argue with success. If it works, enjoy.
But in an effort to better understand what is going on, consider the following. The baking stone behaves like a pot of freshly brewed coffee in a typical inexpensive coffee maker. Just after the brewing takes place, the coffee cools until the thermostat kicks in and the burner clicks on. The pot heats, cools, heats, cools. There really isn't any uniform "equalizing" going on. Heat is always flowing one way or the other. For any given spot (finite element) heat is either flowing away to a cooler spot or flowing in from a hotter spot. Turn off the flame and the stone/platter assembly gives off heat. Assuming the air is cooler than the stone, all surfaces exposed to air cool as heat flows away from the warmer center.
A better way to equalize the stone temp would be to put it in an oven at 700 degrees for a long period. Even then there will be perturbations about the norm, but it beats Blackstone on, Blackstone off.
One problem with the BS dial is that it doesn't handle fine adjustment very well. With the 10psi regulator wide open, my setup struggled to stay below 700F. Adjusting the dial and regulator is a fiddly operation, but if the surrounding hot air is generally 700F, then eventually the stone will be as well.
Perhaps someday we will have finer control on the BS valve. (No C.Bob, I don't have any inside info.
). In the meantime, we can use whatever method makes the best pizza (on/off, 10psi/5psi regulator, combination of BS dial and regulator control, or perhaps needle valve, etc).