I was recently asked by a student to explain coriolis effect. How many instructors who have not gone beyond the PPL syllabus would be able to do that?
The requirement is to hold CPL level knowledge not to hold a CPL. If someone wishes to be an Instructor then they should be able to explain Coriolis effect quite rightly. But as has been pointed out, so should a PPL.....
The ICAO requirement to teach is to hold at least the licence being taught for.
Just because someone chooses not to do a CPL does not make them any less a candidate to be an Instructor and most experienced PPL's make much better instructors than 300hrs hour builders.
The change is currently being pushed through the EASA system which is going to be great news for continuity for students and flying clubs and will hopefully help see standaards improve.