It was a rule drummed into us in training, never to walk through the prop arc of a piston engined aircraft. At Northolt the B17 and Lancaster arrived one day and crowds gathered to admire them as they parked. I stopped one WRAF Officer from walking under the B17 through a prop arc and just as she was about to give me the "Don't you shout at me Mr. BS!" treatment, there was a bang and the prop kicked over. She left in a hurry, presumably to change her underwear.
If I remember correctly, the Spitfire and Hurricane had a big button on the lower right side of the instrument panel for shutting down the engine. I suppose this worked as you describe, by opening the manifold and preventing the engine drawing in any fuel, so it would stop without any fuel charge left in the cylinders.
Old aeroplanes, like my Grandmother, have loads of character and they kick when you least expect it.