I do not doubt AW's cells are the best! However, it's nothing personal . . . this is a characteristic of the chemistry of these batteries. Heck, it's not just batteries, even your 110v house voltage will drop under load! It's simple electric theory at play. I'm sure better cells won't do it as much as others but I'm only talking in generalities. AW himself will agree with what I'm saying here. Do your own tests on a bench with some kind of load and watch what happens.
Another thing . . . lithium ion batteries aren't that crazy about being cold. Ever notice your cell phone and laptop performace if you leave them in a cold place (like your car, outside in the winter) for a while? This is not to be confused with the CR123 lithiums . . . they have a different chemistry and do much better in the cold. I'm talking about lithium
ION batteries. If you get into RC vehicles as a hobby, you'll get to meet lithium polymers. Those like the cold even less and make a lot more fire when you abuse them! Lots of fun videos around of mistakes and experiments with those babies! Be glad you don't have to mess with
those!