So, fake news will be shared with copy-paste instead of forwarding? This will absolutely deter those rascals who manipulate their platform and multiply user engagement.
Much of the current problem is that fake news spreads faster than moderators can make a decision on it, or journalists can fact-check it. If you can keep it in a "slow burn" phase longer, where it's being forwarded along to a handful of people at a time, it's easier to combat.
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.
This seems like it could only be implemented client-side. It also seems like it would require rapid and frequent updates to the ever-growing blacklist. That in turn would require a way to figure out what hashes needed to be blacklisted, which implies either less-than-ideal cryptography practices or the ability to decrypt messages. Neither is desirable for user privacy.
I have a rule I use in computing: whenever you think you want a blacklist, you probably want a whitelist.
Anecdotally, I was in one group and one person announced that they were leaving, so they spent some time saying goodbye. Almost at the same time, someone else forwarded a meme post along the lines of "Sometimes the best way to let go is to tell them to FUCK OFF!"
Well, that was quite funny at the end of it, but still.
The forwarding is effortless and is essentially broadcasting. You don't see the updated conversation from a forwarding screen, so you can't pause to reflect the same way you would if you were typing away a message and seeing the chat flow by. So these messages propagate mindlessly.
To that extent I don't think fake news/disinformation is the real problem. It's virality.