There arent two types or levels of REST. There are just Components that support HTTP to various degrees and that is where the problem lies.
For the most part we are trapped in Browserland HTTP:
- Availability of only a subset of the HTTP methods (GET and POST).
- Visibility/Awareness of a subset of the REST Data Elements (resource identifier and representation).
- Limited or no control of conneg on the client side.
- Broken HTTP Authentication Interface.
- No true client-side state.
The people making the argument that Browserland HTTP is "what’s been proven on the web" and REST is just theory, "speculative", "unproved in practice, and unlikely to be a game-changer" haven't been paying attention.