Good point. I actually was standing to the side of the car at the time and did think about what would have happened to hands, faces, or any other body parts that might have been in the way. Sort of like what happens when you get your fingers too close to the fan or belts when the engine is running only slower.
As for the need for air pressure, I agree it isn't 100% necessary as I ended up doing the two cylinders that kept spinning the engine without it to avoid further damage. However, it does make re-installing the valve spring and keepers a little easier as the valve stays up at max height (fully closed). The air is also very helpfull when you get ahead of yourself and remove the keepers with the cylinder not quite where it should be...
. Watching that stem drop to just below the top of the guide was close to a heart attack. Fortunately I reconnected the air and was able to coox it back up. Pulling the head just wasn't in my schedule for this week.