That doesn’t look like it does a very good job. He should get a friend and each of them take hold of one side of a lawnmower and walk it down the hedge. It would do a better job.
Hye if the guy wants to be stupid at least do a good job of the job at hand.
Agree not only does it nearly get you seriously hurt it does not even trim the Bushes right. I’m sure it’s all gimped up afterwards.