I would encourage you to always question information you have been given if it is unclear or seems wrong - there is a lot of misleading and incorrect information out there, and using your own judgement is an excellent idea.
When you supply extra heat in the coop the (relatively) higher temps allow more moisture to evaporate, increasing the humidity. When this warmer, moister air mixes with colder, drier air it leads to moisture precipitating out onto surfaces (including combs), then freezing - this also shows up as frost on the inside of the coop. Keeping the air temp above freezing would probably keep that from happening, but that would be very difficult, and likely expensive, to do in very cold weather, and would probably lead to air quality issues as the coop would have to be tightly closed. In addition, if you have a power outage or your heat source fails and your chickens are used to it, the resulting cold can be even harder on them to cope with.
When you supply extra heat in the coop the (relatively) higher temps allow more moisture to evaporate, increasing the humidity. When this warmer, moister air mixes with colder, drier air it leads to moisture precipitating out onto surfaces (including combs), then freezing - this also shows up as frost on the inside of the coop. Keeping the air temp above freezing would probably keep that from happening, but that would be very difficult, and likely expensive, to do in very cold weather, and would probably lead to air quality issues as the coop would have to be tightly closed. In addition, if you have a power outage or your heat source fails and your chickens are used to it, the resulting cold can be even harder on them to cope with.
