Alternative priming method?
 

Had an instructor tell me that an alternative way to prime both carburetted and fuel injected C172 models is to simply set the mixture to full rich for awhile before start due to the gravity feeding. Also that if left in anything but idle cut off for too long, the fuel will keep feeding to the engine and would flood it, pooling beneath the aircraft.

It seems a bit crazy to me that it would be designed so, espescially since I haven't read or heard any kind of warning from cessna or anyone else along the lines of "the mixture will flood the engine if left on when it is shutdown".

Can anyone verify/dispute these claims?

Comply with the approved procedures as set out in the
Aircraft Flight Manual or equivalent document.
The manufacture probably knows best.