Are you trying to address a specific issue or just asking in general? If you are trying to address something specific maybe we could offer other solutions.
Have you ever wondered why chickens need room? Some of that is why you might occasionally want more room. If you are constantly bumping into someone or they are in your personal space (or you in theirs) somebody might eventually get irritated, even if you like them. If someone irritates you or is a bully a little separation might be a good idea to avoid conflict. Extra room helps with behavior issues.
The more they are squeezed together the more the poop is concentrated. That means you have to work harder to manage it. Extra room gives you more flexibility in managing problems that arise. More room makes it easier on you.
If you follow the link in my signature you can maybe see why I don't believe in magic square feet numbers for chickens. There are just too many factors involved for any square feet numbers to work for all of us.
If you are addressing behavior issues a space up high can help them avoid each other if they are in conflict. Many people recommend having something like that when you are integrating, it can give the weaker a way to get away from the bullies, especially if room is tight. It may create other issues. They may want to sleep up there or lay up there. You may bang your head on it if you try to work in the coop. Like everything else there are pros and cons. I don't know which will outweigh the other in your unique situation. If you want to use it to shoehorn more chickens into a tiny space, well it's not something I'd do.