I think these articles could add to the overall understanding of the RS:
Here's an excerpt below that I find illuminating:
If you limit yourself to exploring only the conflicting relationships, ¾ of the ways in which people actually relate will not appear in your characters. What’s worse, if you also limit yourself to using only negative conflict, 7/8 of real relationships will be missing in your story.
By exploring all four kinds of relationships in both positive and negative modes, your characters will interact in a full, rich, and realistic manner.
Keep in mind: believable characters are not only built by developing each independently, but also by how they relate one to another!
Conflict is important, but I think that the RS adds dimensions beyond just creating conflict. That's part of it, but not necessarily all of it.
Interestingly, the PRCO of the RS will most likely be objective PRCO defined by the author. This is where the relationship is... this is where I need to take it to make the commentary that I want to make. This is the C that is needed to explore these concepts. This is the R that will illustrate it best. Here's the beginning state of the relationship. Here is where it ends up.
A subjective MC PRCO and a subjective IC PRCO should create the conflict because they aren't on the same page. The RS seems almost like a commentary that enriches the MC and IC but is independent.