The author gives WebDAV as an example of a good standardized REST API. Is adding new HTTP methods (like PROPFIND, MOVE, COPY, etc.) considered to be RESTful? I

The author gives WebDAV as an example of a good standardized REST API. Is adding new HTTP methods (like PROPFIND, MOVE, COPY, etc.) considered to be RESTful? I always thought you were supposed to structure all actions around the main 6, and add extra functionality in the data payload or query parameters.