It's not 'compliancy' as much as they're reinventing the wheel.

REST was born out of a philosophy that the HTTP protocol already solved much of what you wanted to do. HTTP not only solved this, but solved this a long time ago and with 'great success' (aka The Interwebs ;-)

- Authentication mechanism

- Operations (CRUD) -> GET, PUT, POST, DELETE, ...

- Caching -> Use HTTP caching mechanisms...

- Resources -> URL's

- Formats -> mime-types + use a HTTP Accept: header

- ...

They reinvent the wheel on many of the bullet points above: custom operations, custom format handling, custom authentication mechanisms, ... That's why this really is one of the worst implementation of an 'RESTful' API