It does? From Telegram's documentation, it looks like it's still using AES IGE. Telegram, meanwhile, can as far as I understand it encrypt only one-to-one private messages, not groups, and does so on an opt-in basis, in part because their "standard primitives" don't support the usage model of modern secure messengers, which do multiple levels of cryptographic ratcheting using actually-standard KDFs, hashes, authenticated ciphers, and authenticated elliptic curve key exchanges.

Further, outside of Signal, whose authors won the RWC Levchin Prize for their design work, the other modern secure messengers essentially don't roll their own: they draft off the design work Signal did. Which is a good thing for their users. The alternative course, of coming up with your own special snowflake crypto, gets you papers like the one we're commenting on.