interesting link, but the engineer in me fails to see how the aluminum foil "deflects heat to the sides to cause convection"
I'm not Bill Nye, but I'll try to explain as I understand it (scientists, please feel free to correct me).
The flames of your top gas-burner aim downward.
A sheet of foil (or a baking sheet) blocks the gas-forced airflow/heat (maybe not all of it) that would normally go downward,
protecting the top of your pizza from burning,
and since the heat can no longer go straight down to burn the tips of your deep dish crust,
it has to go somewhere else, right?
So the idea is that the gas-forced heat bounces off of the foil and back to the top (and/or sides) of the oven,
and is then deflected (or redirected) until it travels around to the sides.
I would call this redirection of a closed heat system convection, but it's possible I'm not using the term right.
If I'm not describing it correctly, I'll be happy to revise the photo/graphic, but my basic point is that heat which is no longer hitting the top of your pizza gets redirected to the sides and bottom.
Regardless of what it's called, that is what happens when I bake my pizzas with this configuration.