I think this is confusing different levels of abstraction. It's certainly true that more or less any system can be turned into a sequence of 'procedure calls' w

I think this is confusing different levels of abstraction. It's certainly true that more or less any system can be turned into a sequence of 'procedure calls' with appropriate arguments and return values. You can make the equivalent argument that OO is just the same as structured programming, or that functional programming is just a form of assembly language. There's a sense in which it's correct (i.e. that it's possible to implement one with the other), but it's definitely not the right way to think about it. REST is about working with state objects that live on other servers. RPC is about getting other servers to do actions. They're different ways of thinking and coding, despite the fact that yes, you can wrap an action up in some state, or that most actions will be modifying remote state.