I am actually going to ask a TM when we are there in two weeks because my 12-year-old hates this. We've seen the SA cross the queue after coming out a door on the left and going into the little "island" in the center that you walk around. He was wearing a huge black cape with hood and did not jump out that time. This was around 10:00 AM so maybe that's their starting time?
Other times, I have my kid walk on the left and look to the left. It has worked every time except once when my wife looked to the right, saw the SA just standing there with his arms crossed, and screamed. Then the kid screams! It was pretty hilarious, but they are just not into that stuff (they don't do HHN, obviously).
I need a way around this - we'll ask, and try the backstage tour as well.