While I agree that India is not a nation in the sense of the article, India had already been under varying levels of political union prior to colonisation, unless we consider the Mamluks, Mughals, etc. as colonisers in the broadest sense. In fact, I've often heard the truism that the post-colonial effect on the Indian subcontinent was not so much characterised by the artificial federalisation of nations, but rather their artificial separation—in India on the one side, and East and West Pakistan on the other.

Federalism doesn't contradict being a nation-state, India is clearly moving to a more nation-like model under the BJP.