I understand completely where you are headed with this. My years long experience with the 2Stone also lead me to feel that, at higher temps, the bottom would torch off way before the top was there. I think a less conductive bottom stone might help. Also, Larry's recent post concerning a "Chaufelctor" is intriguing. More direct top heat. Many of the Blackstone folks put washers under their stones to try for some insulation (air) between the heat source and the bottom stone.
Conductively is not hard to understand. Simply put, different materials transfer energy at different rates. Do this (thought) experiment: Tonight, water here in Denver boils at about 202 deg F. I can heat my oven to about that temperature and stick my hand in it in the air and will be good for a few seconds or more. I wouldn't do the same with a pot of boiling water.