Unless I missed it, the author doesn't seem to provide an argument as to why the function is exponential. It just seems to be a rant about how much state there

Unless I missed it, the author doesn't seem to provide an argument as to why the function is exponential. It just seems to be a rant about how much state there is. Sure, there is a lot of state, but much of it is "gated" and you don't need to program an exponential amount of logic to get it all to work. To me it's more like UI is the art of turning f(states^n) into f(n*states). With clever modularity and some intuition about how users think, it's a feasible optimization.