Hi Richard,
You asked, "Does anyone heat their oven to 50F/10C (plus or minus) above
the baking temperature prior to putting the bread in the oven, spritzing,
etc. and then immediately lowering the heat to the normal baking temperature?"
Yes as a matter of fact, I do and the reason is exactly as you guessed,
when you open the oven door to put your loaves in it lets a lot of the heat
escape, so preheating to about 50 degrees over allows you to have your oven
at about baking temp when the door is once again closed.
It's important to remember that in a brick oven most of the heat is stored
in the brick itself. In engineering terms that's known as a heat
sink. The brick has great thermal mass giving it good heat retention
capability. Opening the door on a brick oven therefore has little effect
on baking temp. The home oven, however, has very little thermal mass and
you are mainly baking with hot air. Each time the oven door is opened a
lot of the hot air is replaced by cold air and after it is closed again
that air must heated back up to baking temp.
Hope this helps and...
Happy Baking!!!
Don