Selby doesn't adjust his aim when he's down on the shot - the line of the cue does not change. His head moves a little from side to side when he's down, but this movement seems to be synchronized with his preliminary feathers. His cue moves back, his head moves a little one way, the cue moves forward and his head moves a little the other way. Whatever it is, it's not a pivot of any kind and certainly not a pivot-based aiming system.