A few years back we went to the priority gate at Schiphol, unaware that they were operating a pen-like system. The GA swung a gate which effectively stopped an economy pax who was legitimately passing through, dead in his tracks with a barrier in front of him, to allow us to pass through.
It was quite embarrassing to my wife and me and I decided that if a similar sheep-pen traffic system was in operation on subsequent flights, I would rather go to the back of the economy queue.