That is false. Citations please?
'and Bengali speakers'
This ignores the fact that Bengali attained its status because of British who ruled India from Calcutta and enabled Bengali hegemony. No native speakers learned Bengali as second language in rest of the undivided India. Only Bengali diaspora moved to different parts of country as part of British civil services.
'Hindi... was given a formal status of national language by the predominantly Northern Indian Congress government post-independence to use it as an instrument to exert central political influence on the rest of the country'
Another propaganda. Hindi-Urdu (or Hindustani) was the most spoken and widely understood language in undivided India. Hindustani was official language of British. It might lose to Bengali IFF one divides it into Hindi and Urdu. But that division happened AFTER independence, when the spoken Hindi was standardized to a Sanskrit base, and Arabic-Persian words were mercilessly pruned-off to enable non-Hindustani speaking people to grasp it easily. The only people who got the short end of the deal were Tamil, because Tamil language has got almost (almost) nothing to do with Sanskrit.
To blame a newly formed government of an enslaved country, of 'exerting political influence' is the racist tirade Tamils latched on to, after there beloved masters left the country and didn't leave them in charge.