The point that article makes is that good design for the small screen/handheld requires lots of usability testing - making sure that the user interacts easily with the system, doesn't struggle/hunt to find things. Don't just design on a big screen and squeeze it in but use a real device too.

My feeling is that the UI for the tablet probably had several authors so wasn't designed as a coherent whole, didn't go through many design interations, and some features were thrown in for good measure. Love it or hate it, OSX is a reasonable example of consistency!