If the big boss happens to walk by for the 3 minutes you're taking a mental break and that is a problem, I would say the problem is the boss/culture, not the space.
Think about it. You just said that someone "catching you" taking a break is an issue and that in your mind that is a justification for keeping your screen hidden.
Think about it. You just said that someone "catching you" taking a break is an issue and that in your mind that is a justification for keeping your screen hidden.