As to RS being 'just fiber' and Primal Blueprint's Big Ass Salad being enough fiber...that is a point of contention with me. RS has some very specific end-products that aren't associated with most other fibers. RS is preferred food for butyrate producing microbes and when those microbes are allowed to flourish, they cause definite changes to the cells lining the colon (colonocytes) which improves overall gut health, vitamin and mineral uptake, and many other benefits associated with a healthy gut.
The 'fiber' you get with a Big Ass Salad is minimal. Most of the fiber found on a salad bar or produce aisle is non-fermentable by gut microbes, and much of the fermentable fiber is fermented equally throughout the gut by all it's inhabitants.
Fiber that ends up mainly as butyrate includes pectins, gums, and resistant starches. The other fibers like cellulose, fructans, inulin, and the whole FODMAP lineup provide stool bulking properties and some prebiotic action--but don't have the targeted butyrate production that RS has.
The best 'fiber' consumption one could strive for is a mix of all the fiber types, with RS being a majority. Aiming for 40g of fiber per day with RS being at least 50% of that is a good start.