This is dead on. It’s the space between them.
The MC and IC are separate perspectives from the RS, with their own story points. They are related in a holistic sense within the whole big story (entire storyform) but I don’t think it’s a good idea to think of the RS as directly illuminating those perspectives.
EDIT: this concept actually applies better to how the RS is a counterpoint to the OS, kind of showing the alternate perspective to the OS struggles. (i.e. the same way that the IC shows the alternate perspective to MC.) But I think that is a pretty advanced concept and for me it’s something more easily felt than fully grasped.