You're both wrong.
As seen from the driver's seat, one simply pulls on the bottom of the lever. It is spring-loaded and as found, only moves one way.
See the attached image (Mechanical Fuel Shut-Off).
As cmann250 mentioned, with turning up the fuel and hammering it, the increased volume of fuel flowing past the FSS plunger and into the associated orifice, tends to rip a plug from the plunger and sucks it into the Head/Rotor assembly where it either goes into the Delivery-Valve(s) (DVs), or back into the case by way of the Fuel Control Collar.
You said you took it out to show a friend how well it runs (basically
), that suggests you're gonna continue to beef it up, a little more anyway. Assuming that's the case, you'd do well to learn to "Roll Of The Throttle" instead of side-stepping the throttle. The FSS will survive in that setting (with a little modification) and there's a good chance you'll avoid other possible fuel system problems as well.
Just my $0.02.