Actually, the accent is a BIG problem. If he’s from a poor village in Punjab, with little outside exposure, then he’d absolutely not speak any other language than Punjabi/Seraiki. What he’s speaking here is sort of Urdu, in a peculiar accent, which I’ve never heard before from any Punjabi. Also, his facial features and complexion don’t look of a typical Punjabi.
What’s also interesting is that the interrogator is speaking Hindi as spoken in India. I think it would’ve made sense to have someone who spoke the same language/dialect as the suspect, to extract most information out of him. Using words such as “pita ji”, knowing when no-one in Pakistan calls their father “pita ji” is surprising.
Also, from the questioning, it seems the interview was taken the same day the incident took place. However, according to reports, when Kasab was captured, he was seriously wounded, which he doesn’t appear to be in the video.
And why is he called “Kasab”, when the real pronunciation would be “Kasaab”, as in butcher. That he even responds to Kasab is surprising.
In the end, they may determine he’s a Pakistani, but the evidence in the video does not corroborate the claims about his identity.