> I am Hindu, and I have no idea how you got this off track
I have studied Hinduism and India in detail. I'm sorry that you feel my analysis is incorrect, but I can try to explain. Firstly, the census data you linked to still relies on the British definition of "Hindu". It may come as a surprise to many Indians including those that would describe themselves as "Hindu" that in fact, the term Hindu was popularized by the British and just meant "non-Muslim". That definition even originally included Buddhists and Sikhs.
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The British government created a compendium of religious laws for Hindus, and the term 'Hindu' in these colonial 'Hindu laws', decades before India's independence, applied to Buddhists, Jains and Sikhs.
Rachel Sturman (2010), Hinduism and Law: An Introduction (Editors: Timothy Lubin et al), Cambridge University Press,
Beyond the stipulations of British law, colonial orientalists and particularly the influential Asiatick Researches founded in the 18th century, later called The Asiatic Society, initially identified just two religions in India – Islam, and Hinduism. These orientalists included all Indian religions such as Buddhism as a subgroup of Hinduism in the 18th century. These texts called followers of Islam as Mohamedans, and all others as Hindus.
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There is little in common with the "Hinduism" practiced in say, Uttar Pradesh with the "Hinduism" practiced in Kerala. In Kerala, Hindus even eat beef from cows which would be considered a sacrilege in Uttar Pradesh. This is why the term Hindu does not really communicate any information other than "non-Muslim" and even that is debatable since parts of the "Hinduism" practiced in places like Rajasthan bears a great deal of resemblance to Arabic-Islamic culture.