The Yes, Prime Minister advice is different. That 4-stage formula is for ignoring a crisis. The PM's No is advocating for working on tickets in priority order which will result in following the plan under a remarkably large number of situations. The two major differences are firstly that the YPM steps don't involve priorities at any stage. And secondly, the PM's No is a straightforward but a polite way of pointing out that the work being asked for is very low priority and so is unlikely to ever get time assigned to it.