Local collision handling is best utilized in a one-to-many collision scenario, for example one player object which may collide with multiple enemies, power-ups, etc. For local collision handling, each collision event includes a self table ID, representing the object itself, and event.other which contains the table ID of the other Corona display object involved in the collision.
Nowhere does it say self is required, it says it’s included so you have a choice of using it. Either way your suggestion did not work and was also the first thing I tried.