Why not using it on DELETE and PUT data while calling Security::clean_input() ?
It could be useful for REST API to have a lighter weight code
(yes, I'm a lazy worker, and so what ?)
Currently there is no easy and standard way to extract PUT and DELETE data, you will have to fetch and parse the raw http input data.
The way you parse it is application specific, so it's up to your app to do that, and then to call Security::clean() to clean the array containing the parsed result.