Chicken keeper here. Free range chickens can involve barned chickens just able to move about I think, so not caged, free ranging.
So free range may not be outside, in the fresh air all of the time, or at all. But this differs from enterprise to enterprise.
To also put it in perspective, I’ve rescued huge lovely girls, all fully feathered, as were all their hundreds of sisters, from an organisation which regularly rescues chickens, on more than one occasion.
And some chickens go through a huge moult, the first time this happened to one of my girls, she looked like a fresh or frozen chicken running around the garden, I was horrified, but it’s normal.
Another factor is that farmers get rid of their chickens when they stop laying so much , which is when they also first come into moult.
They will start laying again, when their feathers grow back.