First chickens feet are not designed for prolonged perching with toes wrapped around a perch. But that aside, in the winter they are able to have their feet flat and sit on them preventing them from getting frost bite on the toes.This is probably a newbie question, but why don't you want them to have to wrap their toes around the perch?
Chickens are unlike parakeets/parrots who like to 'curl' their toes around a round roost bar. Chickens ideally need a 2" x 4" laying FLAT so they can lay on their feet comfortably...they don't like to curl their toes. Also, during the winter months while laying on their legs/feet they stay much warmer, can balance themselves better, and won't be as prone to frostbite.
