Try that same scenario in a driving rain storm in Seattle, WA at a sawmill in the middle of the night that we were trying to get back up and running. I went backward off my ladder from about 12-15 feet in the air and landed flat on my back in about 4" of water with anchor bolts sticking out of the concrete on each side of me. A few inches to either side and I would have been impaled.
Grounding is very important for the supply at the wall, the machine, and the people working in the area. Not sure if the ground would have made much difference when I was soaking wet from head to toe and there were several welders and other equipment operating. It was just a bad setup all the way around.
But if the 120 supply in the shop has an entire line without proper grounding it could have taken out more than one yoke and they may not have seen the connection since they were working in differing locations.
Just a thought.
Have a Great Day, Brent