The purpose of the Relationship Story Throughline is to communicate what the single inequity looks like from a WE perspective.
The storyform is a model of a single human mind trying to resolve a single inequity.
By definition, you cannot describe an inequity directly—it can only be described indirectly, from several different points-of-view.
The WE perspective is one of those—and most often, the one most forgotten (go see the latest How To Train Your Dragon movie).
I think this definition is deceiving—it should be the passionate part of the argument, not the passionate argument, as if it is somehow separate from the logical argument. The storyform is one argument—as seen from different perspectives.