While your hands aren't moving, such as when gripping handle bars while snowblowing or mountain biking, you have a lack of blood going to your hands. Therefore your fingers are generating less heat that the glove would use to reflect and keep you warm. I noticed the same thing while digging snow pits for avalanche testing, and had the same initial thoughts as you did. In order for almost ANY glove to keep your hands warm in freezing temperatures, you need to have some sort of movement going on. Hope that helps!

I understand your point about circulation as I have CREST syndrome. One of the five symptoms of CREST is Raynauds. I have had other high end gloves that performed much better than these at far colder temperatures (-20 F) and those gloves cost less than these. After giving these gloves a try my review stands as is "Not worth the money".