I've done this thought experiment before, the "how many apps do I need at once" one, and thought the same.
The problem I have with it, is that it doesn't hold up in real life. When I work with a desktop, or a countertop, or a workbench top, or any sort of work surface, I don't allocate a single rectangular area, and then set up my cooking utensils, or books, or tools, or whatever to occupy those perfect proportions that you describe. I shuffle stuff around, I pile stuff on other stuff, I unearth things when I need them again. If I was really obsessive, maybe I could work my tool bench in the garage the way you describe, but reality is, I wouldn't.
I think one of the reasons the desktop metaphor has been so lasting, is that it *is* a metaphor for a real world experience. It may be suboptimal and innefficient compared to what I could accomplish if I'd just organize everything just so. But it is a method of work management that I gravitate to again and again. I seem to be able to work that way instinctively. And because it is so approachable, as disorganized as it might seem, it actually works well for a computer interface because I've optimized in a million subtle ways how to work that way.