This advise isn’t using newer recommendations for chicken keeping.
Mild frostbite is still frost bite.
Frost bite can be avoided if you keep the coop above freeze and reduce the moisture levels in your coop.
They have studied and shown that is idea of Re- acclimating isn’t doing anything for symptoms of cold stress in chickens.
Chickens bodies show cold stress at 55*-60* F and the signs of being cold do not correlate with the bodies response to cold. I would look up how cold stress effect a chickens body and see if you are ok with that. They have found that exposure to 60F during egg cycle causes egg yolks to have a toxin. Reading these studies as convinced me to make sure my chickens aren’t in constant stress.
modernpoultry.media/cold-temperatures-can-have-severe-