So many things come into play for staying warm in very cold conditions.
In the books you linked they cover them pretty well.
Balancing cold temps, body activity, perspiration levels, calorie intake, and physical condition, all come into play.
If you were outside at -40c with 10 inches of loft insulation fully around your body, with no activity, and no food intake, you would slowly freeze to death.
When moving you need less insulation due to increased activity, if you have to much insulation you perspire, wetting the insulation and causing failure. When you stop you add insulation to make up for less activity.
It is the same with footwear, though in very cold temps without excess insulation your body heat can push moisture to the outside, with breathable layers, and freeze it off on the surface of the boot or garment.
You may still capture moisture in the inner layers and need to change them to stay warm.
Another way so keep the moisture from your insulation is a vapor barrier, sock or clothing, but that is a whole learning curve on itself.
I do use vapor barrier sox in my boots, all types, at times when I need to keep the insulation dry from perspiration, it works best in 0f and below for me. but you need to do more foot care at night to avoid immersion or trench foot.
Time spent trying to decode the books you attached will help a lot in understanding the interactions.
Hope that helps