Scrubber,
Yes these are the design criteria for NPAs - just like the requirement to abort an approach if you fail to remain established inbound (+/- 5 degrees). They are not only a number surveyors and approach designers use to "build" an approach, they are also a legal limit.
Exceed the limit for any given descent and you are outside tolerances. Which equals missed approach.
It's not a difficult concept to grasp.
