I think he meant that only Telegram would be be blocked instead of possibly affecting half of the Internet on the way there. For Telegram it wouldn't be any better.

They would still be blocking the IPv6 netblocks assigned to Amazon and Google, only it would be easier because the blocks would be more contiguous.

I'm assuming it would be easier having one IPv6 address used only by a single application, that's why. Amazon/Google services would be less affected then. There's a whole different question if government would bother to be that precise, still.

The whole point of moving to the cloud was to make themselves harder to block. I don't think they would self-defeat by limiting themselves to a single /64 or something.