Francis Fukuyama in his recent book “The Origins of Political Order” makes a similar claim about the origination of the rule of law, and so says that India has actually long had it because Brahmins held the state accountable to a set of laws that the king did not create. However, he finds that India never developed a strong state (like the Chinese did, who on the other hand, never had the social stratification necessary to create the rule of law).
Kar spends most of his articles going into quite detailed arguments about why the Harappan civilization must have been the originator of the Indo-European language group. He notes that the only societies to develop large-scale civilizations and state apparatus only came from a relatively few language groups (and almost all of of the major ones from Indo-European or Sino-Tibetan). Although there might be something to the idea that language groups would also pass on and share ideas about political ordering, it seems overly determinative.
Still, I think it is noteworthy that both Kar and Fukuyama bring their rule of law historical genealogy in one way or another back to ancient India. I think these two pieces represent a broader movement in the academy that has been going on for some time to show that the origination of industrialization, the scientific revolution, or the modern nation-state in the West was less a sign of exceptionalism and instead a tweak or subtler reshaping of a more broadly shared heritage of ideas. This has obvious political ramifications. How one tells the beginning of the story (in this case the story of the rule of law) effects each other piece of the narrative up to the present, as well as arguments and justifications for what the next step in the story should be.