That is a point in favor of selecting cold-hardy breeds of chickens, if a person lives in a cold climate.Man has NOT been modifying wild birds genetic make-up to make them produce more "perfect" eggs, to have larger drumsticks, breasts. We control chicken breeding and in many instances weaken their sturdiness with those practices.
We have domesticated the chickens. Wild birds survive through "natural selection".
It is not a reason to assume that all chickens need supplemental heat at the same temperatures.
For any given person, watching the behavior of their own chickens will give the best information about what temperatures are comfortable for those chickens. If some chickens sit around with ruffled feathers on days at a certain temperature and perk up on warmer days, those particular chickens were uncomfortable at that particular cold temperature. That could be a good reason to offer a heat source, so the chickens could choose a warmer temperature when they feel cold.
