The 'hype'?
Believing that 14 F is cold is no hype - it's a solid fact and not an exaggeration. And, yes, of course that I don't try things like camping in the cold without a tent or a sleeping bag - I am old and old people, if nothing else, learn that doing things to 'try them out' is not the wisest thing one can do.
Yes, birds do have mechanisms to maintain' their internal temperature constant - all endotherms do and the safe internal temperature range is actually very narrow, an average of 5 F. They shiver, they fluff up, they eat more and they move more. But these mechanisms were never meant to remain 'on' for months and months and, if they do, their bodies suffer. For one thing, a fluffed up bird does not fly (feathers need to be slick and tight against the body for this), for another, keeping a higher metabolism by eating more just to keep the body warm enough for homeostasis takes a huge toll on their telomeres (all physical stress does). Birds already have a much higher metabolism than mammals (70% higher) so keeping it at an even higher rate for months means shorter lifespan (as well as compromising basic functions like breeding, digestion, sleep, etc).
And yes, I know that you are trying to keep them warm
I just don't think you are going about it the right way, I think that you are leaving too much up to chance. Please understand that, when it comes to bird care, I go to the extreme. I strive every day of my life to give my birds the closest conditions to their natural habitats, diets, social needs, etc. and part of that is ambient temperature.