From personal experience, this is not really true, there are some languages that do maintain some sort of mutual comprehension, but the vast majority in India h

From personal experience, this is not really true, there are some languages that do maintain some sort of mutual comprehension, but the vast majority in India have no guarantee of that apart from a few choice root words. Speakers of a particular Dravidian language will almost certainly not be able to understand another, and you could make the same argument for Indo-Aryan languages with a very high percentage of success. It's like calling English and French the same language because they have some words that have a similar root. Or even English and German.