Don't they already have the capability to hit all of India, though?
Well yeah, their ballistic missiles can hit most of the Indian mainland.
Makes perfect sense to have such a weapon,if you are a Paki.The specs of this weapon put this roughly in the class of the Tomahawk,not larger weapons.You can modify the torpedo tubes of their Agosta 90Bs or surface ships to fire those & upto 4 such weapons can be carried on those subs.It completes a poor man's nuclear triad!!
Their ballistic missiles are too cumbersome for launch from anything other than land platforms,reducing range & increasing it's vulnerability.