Bilal bhai what you are terming as India's strategic depth is India's strategy not geopolitical depth. Strategic depth for Pakistan is that in a war India will capture large land masses of Pakistan, so in order to mount a counter offensive the Pakistani corps will move backwards into Afghanistan and consolidate their position. The idea was started by General Mirza Aslam Baig. The main reason being the slim baseline of Pakistan. In order to counter this India's strategy is to make Afghanistan stable and insulate its sovereignity from Pakistan. India cannot have strategic depth even if it wants because of geography.
Bhai, the article clearly talks about strategic depth:
Strategic Depth, Strategic Assets and the Changing Dynamics of Pakistans Kashmir Game Plan
Please refer to the heading of the article, & the definition of strategic depth they used for Pakistan in the article. By the same token, a similar definition for India's strategic depth can also be established.