It's a good idea to treat EVERY engine like a loaded gun.

I always treat my gas engines like they are alive and could cut me at anytime. If I'm working on it, the ignition battery is unplugged. If I'm flipping it I make DAMN sure I know when the switch is ON and when it's OFF.

I've seen an ignition system release one more spark AFTER it was turned off. I switched it off and grabbed the prop firmly. Turned it over very slowly and watched the spark plug pop one more time. Just because the ignition is off doesn't mean you can get lazy or treat it any different than you would if it was turning 8000RPM.