This is a huge simplification of the history of the Indian subcontinent. The British are the architects of the new boundary lines, but they are also the architects of what is now a unified country, India. Indian subcontinent as a unified entity prior to the arrival of the British as a major colonizing force in India is a lie. India was quite divided before that, which made it easy for them to play their little game of "divide and rule".
None of this absolves them of responsibility, but this over-simplified statement irks me, as it is a gross misrepresentation of the politics of the Indian subcontinent prior to the British.