Oh, that's nothing. I've seen a shove move past a photo line with no one on the rear of the train at all. On another occasion, I was told of a shove move past a photo line where it was decided that the engineers would swap out during the move. One engineer dropped off the moving engine, which rolled on unattended until it got to where the other engineer was waiting to hop on. I guess that they were demonstrating old time railroading.
As the other poster said, it depends on the operation. Some are very professionally operated, while others make you cringe, and even the professionally operated ones have bad days and mind farts.