Without really trying to think this one through,which maybe one of the physicists out there will,we are maybe talking about conductivity or heat transfer?
i.e.,does metal attain/achieve heat/temperature differently at different altitudes,with a constant heat source?
We are not talking about water boil temp.,unless we are trying to fix chicken skin.
The internals would always be below 212� and would also be affected by the impurities in the water[brining]?
Someone's experience,like Matt's,is usually better than the science-in bbq.
I agree with the others,when I can pull the bone out of that shoulder,I can run a toothpick between those ribs,and that brisket slides off a meat fork it is probably done.
Some days it takes one more cold beer than another.