cockpit of a mig29

cockpit of a Su27

In several russian fighter jets ( MiG29, Su 27 ...) there is a white line on the stick that match with another one on the canopy. Is there any reason for this ? A former flight instructor told me that it was to help pilots to recover from a spin : When the two lines match, the stick is in the good position to stop the spin. Is it true or is there any other reason for that ?