It also seems like a valid and useful way to slow the rate of propagation of real news. Real news also spread very fast and faster than moderation.

The point is, this has next to zero selectivity. It just makes the platform hostile to encrypted group messages. My guess would be that (besides PR regarding the Indian stories, which is a social problem, not a technical one) this is about censorship. You can't censor things you can't see. Better stop them from communicating freely.