This is the way I cook and I have never experienced this, I guess I have been lucky all these years!
Only sear first if you want a thick layer of gray, overcooked meat.
Me too. Never had any gray on a quick hot sear first.
Scientifically, you'll have less gray meat with the reverse-sear method. By starting the roast out at a low-hot temperature (250 or less) for a couple of hours, the outside of the roast will already be warm to hot and dry prior to searing. Searing already hot and dry meat will take less than half of the energy as cool, wet meat.
Searing first requires that you heat the meat up from fridge (or room) temperature to 310 degrees (which we all know is the temperature that the Maillard reaction occurs). Add this larger temperature differential with the fact that way more moisture still resides in the far outer layer of the roast and it's simple to see that it'll take far more effort (and heat and time) for a proper sear.
I'm not saying that you cannot achieve great results any other way than the reverse sear (I've cooked wonderful prime ribs before I've "discovered" this method). I am saying that if you want to diminish the gray layer, the reverse sear is your best bet.
