Essentially: it's not designed as a change from North/East/South/West, it's designed as a from-scratch way to refer to those directions.
The sun rises in the East and sets in the West, so let's say East is "Sun" and West is "Setting-Sun."
Polaris/The North Star is in the North, so let's call that direction "Star" and the other direction "No-Star."
When you say "Setting-Sun-Sun-Star," you're saying the direction is more similar to the path the sun takes through the sky than it is to the North Star, and in the direction the sun sets.
16 directions is pretty arbitrary anyway though, usually 8 is enough and then you don't have the confusion of repeated words.