This depends on the definition of "Hindu".
From strictly religious/cultural angle, certainly not true....from basic fact that there is no dogmatic crystalised definition of "Hindu" to begin with (in the sense that it is often used with the abrahamic religions and certain other cultural systems and identities too).
As a Hindu myself, I am often extremely different to a Hindu from another part of India (or even same part of India)....in very deep ways. You can get extremely different answers (each with written, defined, practiced and inherited basis) for questions that other religions and cultural systems have long settled and made quite clearer bound wise.
This descriptor origins was at root geographic (Hindu, Hind, Indus, India, Sindhu, Hindustan etc etc)....applied to a whole variety of (downstream amalgam of various indigenous and introduced) belief systems.
The other (popular) name is Bharat which is more "original" dynasty based much like the name of Qin emperor in China.
The modern republic certainly was not formed on religious (majoritarian need) basis.
A very large number of muslims stayed within India during partition.....they are as part of Indian identity as any other minority, plurality or majority found within it.
The original (attempted and ongoing) definition, push + sustainment for religious based majoritarian state lies on the Pakistan side in subcontinent.
That has had some counter-influence on India downstream due to whole number of matters.....but that is different subject to get into.
But the Indian republic at its core is not any kind of exclusivist religion identity (or really any kind of identity other than the geographic bounded one and all the deeper legacy it has contained within it nation-wise over a long time).....
....just like Turkey is not either (and it has similarly seen a recent realised drift in various way over time from its initial visionary setup as well).
Those are significant counter-counterforces (versus the drift in a chunk of years) by having the core set up this way as well.
Thats pretty interesting man.
I know India is diverse but never knew they were this diverse when it comes to being Hindu.
Not to mention you have Buddhists, Jains and Sikhs. Islam, Christianity, Zoroastrianism and Judaism may not be native to India but overtime they also contributed to India and its identity.
India is so diverse from its languages and ethnic groups. North India and South India are also pretty different from each other.
I learn new stuff everyday.
@Ryder Think of it this way...
Say if Iron-age Europe moving forward retained large degree of its various pre-christian belief systems and only partially Christianized due to whatever reason.
We know many of those non-christian belief systems (celtic, germanic/norse, italic, greek, balto-slavic etc etc) were related and coordinated to each other by the neolithic and bronze age era large indo-european migrations (and later influences from egyptian and semitic civilisations as well).
Specifically their (yamnaya) cultural + lingual seeding legacy (especially that being lot more than their genetic admixture impact).
Then say Europe faced all kind of invasions (many of which brutal) at various time from outsiders....and even colonisation by a large power outside it (which say in hypothetical AU....achieved modern era enlightenment era first by reposing fundamental rights at the individual level first.... instead of Europe itself in the current reality....and the power levels this unlocked to do so).
For simplicity + inherited "first naming rights" (re-appropriated by Europe with time too) many would likely cast a dragnet and call the earlier underlying beliefs as say "Euro-ism".
Whereas Europe itself is an immense geographic term etc....and you only would understand the internal belief/identity complexities with enough study and experience of it (including what many traditionally use to call their belief rather than foreign named sense of "euroism" etc).
Then say during modern independence struggle, simply a geographic state akin to the European Union came into being from the top down (politically) essentially....and a religious-polity component (in 2 separated parts even) of it split off at same time for whatever reason (say all kind of frictions coming to a head during the independence struggle).
BTW, something very similar actually exists with China in that its belief systems are called "Chinese folk religions" (by outside looking in) when you simply cast the net on the geographic bounds of China.
They have all kind of variance and their own various long interaction with their ancient domestic "philosophies" (the precise term is difficult to find in translation), i.e Tao and Confucian and the one that spread to them from India : Buddhism (and many others I will not go into).
As small personal example, growing up in HK, there were 3 very popular deities (of that region of China) with the local folk tales encapsulated for it.
But when I went to Beijing and brought it up with some (fairly cultural intensive, folk religion practicing) folks.....they were not really cognisant of any of it past very general terms....being further away from the vast southern coastline and its phenomenon of typhoons and storms..... I understood why the sea deities for example might not have had same impact up north + interior.
Some number did not even know that the larger HK area (pearl river delta) was where the last (tragic) stand of the Song dynasty was made (against the mongols)...and that one Song commander intimately involved in that is deified as a protector and sign of enduring loyalty.
So there is a "southern axis" flavour of culture (incl "religions") that is quite different to the central and northern axis ones of China....very broadly speaking. It is similar case in India too....the sheer distances and (historical) contexts involved.
Essentially, river valleys (and even long river courses) and the expanses between them matter very much in the end for "geographic-bounded" civilisations that incorporate more than one of them.
