A point which is worth mentioning is that when you turn the mags off you are making a circuit by earthing the mag to the engine. This is not fail-safe in the event of malfunction of the "switch" (key etc) so this is another reason why props should always be treated as live.
In short you cannot assume the prop is not live just because the mags are off.
The problem with pilots pulling on the props to move the a/c is usually lack of an appropriate tow bar.