He wasn't (I hope) trying to start that engine. Pulling it through to check compressions, more likely.
Personally I wouldn't hand swing anything with more than two blades.
I've had a 180 Lycoming with a four blade prop start with keys in my pocket, first flight of the day, just out of the hangar, temp -10 Deg C. No prime, mixture lean. Throttle at idle. Chocks in front of the wheels
That was because it was normally a cow to start on a cold day and I wanted to unstick the oil before starting it. Ran for long enough to walk round the wing. That was a broken mag lead.