> REST isn’t about exposing your internal object model over HTTP — it’s about building distributed systems that behave like the web.

I think I finally understand what Fielding is getting at. His REST principles boil down to allowing dynamic discovery of verbs for entities that are typed only by their media types. There's a level of indirection to allow for dynamic discovery. And there's a level of abstraction in saying entities are generic media objects. These two conceptual leaps allow the REST API to be used in a more dynamic, generic way - with benefits at the API level that the other levels of the web stack has ("client decoupling, evolvability, dynamic interaction").