You found an old thread, didn’t you?
You might follow the link in my signature to get my thoughts on space for chickens. People like to think that this is an exact science but it is not. There are a lot of variables.
That “math” you are talking about (4 square feet in the coop along with 10 square feet in the run for each chicken) is pretty much set up for an urban flock of all hens at the same general maturity level. If you have a rooster, have a broody hen raise chicks with the flock, or ever want to integrate new chickens, it can be a real problem. Or it might work out. It’s really not an exact science. In general I find the tighter I squeeze them, the more behavioral problems I have to deal with, the less flexibility I have to deal with problems, and the harder I have to work. I am a proponent of providing plenty of space because it makes my life easier.
To answer your specific question, looking at coop space in isolation isn’t all that important when looking at behavioral problems. What is important is how much total space is available when you need it. If that space underneath is available when they need it, then it counts toward the total.