Sure you could view the UI as a set of "motions", but the argument of this article is about how you could simplify such analysis: just count the number of concepts or elements presented to the user. The smaller the count, the easier the UI would feel.
Bad UIs is the reason I stick with my Palm PDA, even though synchronizing with a Linux box is not easy.
Actually, it's ridiculous how difficult it is to make a simple appointement with any calendar tool, compared to a physical calendar. I tried KDE's, Evolution, Lighthning from Thunderbird, jpilot, Google Calendar. All very complicated, a lot of <Tab>, mouse pointing, and options to get lost in.
The number of tab hits is a better indicator of how many elements are in the interface. Using a mouse, you can often skip past several steps or options. Once you're familiar with the interface, you don't notice how much you're skipping past. Nevertheless, when first confronted with an interface, your eyeballs and brain have to read and process the whole mess. Sticking with Jakob Nielsen-like conventions reduces the user's feeling of needing to examine every interface element. That's nice, but the elements are still all there, and you must "deal with" (author's term) each one when tabbing.
The author says: "There's nothing complex or confusing about iCal's event entry UI. And with specific fields for each item of data, it is more obvious than Backpack's--but only for a first-time user, which is the wrong case to optimize for. But to me iCal's date entry UI is clearly worse, much worse, and the reason why can be expressed by the fact that it forces you to deal with about 10 user interface elements, versus just 2 for Backpack."
In summary, an interface with many elements which follow conventions might be fine for first-time users and those who use prefer a mouse to keyboard navigation. But the author wants an interface with fewer elements--even if their meaning is not obvious--because he likes to hit the tab key, not click a mouse.
http://en.wikipedia.org/wiki/Therblig