There are so many different things that go into space requirements for chickens that there is no one right answer for all. Room means both in the coop and other room available, whether in an enclosed run or with a lot more "free-range" space. If someone is talking about coop space only and ignores the additional space component, they are not talking about the whole picture.
Each chicken has its own personality and each flock has its own dynamics. If you get a vicious brute, hen or rooster, then the others need extra room to get away. If they are all relatively laid back, then they don't as much room. How you manage them plays a part. How often do you leave them locked in the coop while they are awake instead of giving them access to additional space.
Climate plays a part. How often do you have weather that keeps them in the coop? Again, chickens are different. I've had some that will walk through snow and forage once they get used to it, while others would never set foot in snow. Mine generally don't mind cold, but they don't like wind. If the wind is not hitting them, they will go out and forage in single digits Fahrenheit weather. But if they can''t get out of the wind, they pretty much stay inside or find a protected place. Whether they have a place they can get to that is protected against snow accumulation and wind makes a difference.
Then there is the issue with how hard you want to work. Do you want to go out and clear snow whenever it falls, or maybe scatter something on top, like straw, for them to walk on? You'll probably need to clean that straw up later. How often do you want to get involved in poop management? Some people manage poop on a daily basis. I shovel up the poop accumulations under the roosts maybe once every 4 to 6 weeks and just rake the rest. It's been years since I cleaned out the whole coop and that was more to get compost material that because it needed it.
I find that by giving them extra room, I work less and I have more flexibility in how I manage them. My coop is oversized, so if I want to sleep in some mornings, I can. If I want to take a trip, it is easier to get someone to take care of the chickens if they don't have to get up at the crack of dawn to let them out. If I have a predator problem, I can leave them locked in the coop and run (which is also large) while I deal with the problem.
The bottom line is that there is no one set answer to your question. You might be fine with your set-up and that spacing, even if they are trapped in there a fair amount of time this winter. The tighter they are housed, the more likely you are to have behavior problems with them and the more you will probably have to work. I am certainly not going to guarantee that you will or will not have problems. I don't know.
