From discussion in
MDL-28583, Petr mentioned:
"Course format is one of the oldest parts of moodle, it should imo control the whole course page since the very start of the course/view.php, the fact that it does not control output indicates that the API in not good enough for current usage".
There was agreement from the discussion this needs doing as course formats and new format ideas need it.
MDL-28583 for further background on the discussion.