The word "broken" means susceptible to practical attack, and attacks aren't always of the "cryptanalyze the ciphertext and read the plaintext because you're a clever mathematician" variety.
To add, Telegram's crypto is completely and totally off the walls crazy in terms of design. Add to that the fact that there are cryptographic breaks (though not we can read your ciphertext breaks), and you should be careful.
iMessage would have been reasonably secure had they used AEC-GCM or a MAC. The design at least made sense: compose a scheme out of known primitives. They just missed (very important) details. Telegram is just turtles all the way down.
