Yes, I'd expect a bow to be a tad stiffer in the cold.I regularly shoot outside at home, so the bow goes from about 20deg inside to 5 or 6deg at this time of year outside, you defo notice the difference.
This all rather begs a couple of Qs
1. What if the bow was originally tillered in an unheated garage in the winter, it's then actually built for shooting at that temperature!
2. Does anyone actually have a source for the practice that is say, pre 1950 ?