Because the fuel is (theoretically) vaporized, as it's drawn out of the venturi, the moment you stop drawing air, you stop drawing fuel vapor. Sure, there could be SOME small amount of liquid fuel in the intake manifold, and theoretically, it might possibly run down into an open intake valve, but how much? What are the odds of an engine coming to rest in a position where the intake valves are open? I think your teacher is making a big deal out of a very low probability scenario.
Sold the Gnewt.
Bought a boat.