Mr. Christie started at Apple in 1996 to work on the Newton, so he has a long relationship with Apple's touch screens. He was invited to work on a secret project in late 2004, resulting in two meetings a month (in a room with extremely limited access) with Steve Jobs to show progress and get feedback on the software that would power the iPhone.
You may wonder why Mr. Christie, still an Apple employee, has suddenly become so chatty. According to the Journal, “Apple made him available on the eve of a new patent-infringement trial against Samsung Electronics to highlight a key element of its legal strategy—just how innovative the iPhone was in 2007 when it arrived.” Mystery solved! It's all going to come out in court anyway, so Apple is getting out ahead of the story by releasing it themselves.
It's an interesting read, and confirms that a good portion of Apple design is thoughtfulness. How fast should a list scroll? What happens when you get to the end? Someone made a decision about how every single pixel of this new device would be an Apple-level user experience.