Look at it in a broader sense, if they had gained access to chahbahar or iran , even in that scenario they would have always remained a looming threat on our heads.
Lets look at it this way, an afghanistan in ussrs clutches, and india on the other edge, we are squeezed between tow hostile states and india wont hesitate to attack us.
Now assume both afghanistan and iran had fallen in ussrs lap , that would have become an even huge threat, a whole region to the other side of our western border would have been occupied by a ruthless expansionist regime and on the other side an ever ready to attack and wanting to break pakistan ,india sitting would have been far more than ominous.
The access to warm waters statement might have been a very simplified and basic statement to tell the masses abt probable threats posed to our states sovereignty.