This is NOT analogous to horse vs car.

20*F isn't very cold. Like I said before those are "survival" items and would keep you alive, but not very comfortable (as per the companies website). Far warmer than down bags? You et al keep stating this without a direct comparison. Show me a bag which is lighter, packs smaller and is equally comfortable not "should keep you alive in all but the most extreme conditions."

I am not sure you have even read the links you even put. The usage of these bags by the military, as I stated earlier are for trauma cases, to prevent hypothermia. They are NOT the issued sleeping gear for the soldiers.

On the point about Mil-spec. One cannot buy US military gear (except surplus), but Mil-spec is made to the "same specifications" and thus similar enough that one could hardly tell the difference.