It could be a lot of things. We sat on the train itself, at the old hold-up, one time, because they had to drive an ambulance into the park for someone. It got hot sitting there in the sun, not being allowed to get off the train to walk around (which would have been cool). The performers needed a contingency plan for such an event. Finally the conductor read to us from the SDC brochure.
Maybe someone on the train needed such help and they were beyond a point where the arms could be raised. Who knows. You can figure they wanted to raise the arms even more than you did though.
