There are so many differences in our flock make-ups, climate, management techniques, goals, individual chicken’s personalities, set-ups, just everything is unique. You have to be very careful taking what one person says and relating that to your situation. The requirements for a flock of four hens all the same age are quite a bit different than for someone with a flock that contains several roosters, broody hens raising chicks with the flock, and/or always integrating new chickens. I suggest you follow the link in my signature below. It might help you understand better from my perspective.
I always advocate more room. I find I have fewer behavioral problems, have to work less hard, and have more flexibility dealing with problems when I have extra room. I also do not believe in magic numbers. Many people can get by quite well with less room than I think I need. Some people need more. It depends on their unique situation.