Btw. one of the subway drivers explains in the YT comments that NYC had this gesture first, Japan copied it in the mid 1990s.

  Conductors point at the board because it is required by TA 
  rule. This idea was adapted by the Japanese subway in the 
  mid 90's. We point because if the window of your cab is 
  somewhere within limits of that board, it means the Train 
  operator, the one who actually moves the train, has stopped 
  at his/her mark for the correct number of cars the train 
  has. We also have to point because supervision does move 
  around in the field and yes they actually WATCH us to make 
  sure we comply with this rule. If we don't, well then its 
  not going to be a good day at work...