Figures that would be rule number one. Everywhere you go there are pretty UI's that are garbage, functionally.
Animation, transparent fading, no distracting scroll-bars or borders, wrapped around a 1-2-3 menu selection.
> Productivity soars when a computer and its users interact at a pace (<400ms) that ensures that neither has to wait on the other.
That is just nonsense. Productivity soars the faster the computer is. Ideally, the user should never waits for the computer; everything should be instant.
Whether the user waits for the computer is neither here nor there.
The ultimate computer-does-not-wait-for-the-user is to have the users prepare job specifications entirely outside of the computer and then submit them to a clerk at a job window. The computer never waits for a user because the job queue is busy from numerous users. It is not very good UI.
In an actual interactive UI, a needless delay could be caused by, for instance, collecting the necessary parameters for an operation through a cascade of multiple dialogs instead of batching them together. Though the computer waits more, too, that's irrelevant; the user's time is what was wasted.
I'm amazed anyone pretending to be a UI person would even feign being interested in how much time the machine spends waiting for the user.