It's no accident, and I'm really getting to see why this technique works. It's simple. Given you have a days work, working from a short list is do-able. If the tasks are prioritised things get done.
The bit I've found hard: when things interrupt, the old list is useless and a new one can be made to reflect this. It really is a great hack and hearing stories from people who have worked with this is a real confirmation that it can work.