Is it? It says private chats sure, but I believe this is one of those word games where the three types of chats are group chats, private chats, and encrypted chats. As in, I think this is referring to chats between 2 people that are unencrypted. 

Not to say I have much confidence in Telegrams encryption though. 

nerd2ninja

Afaict, this is about those "encrypted" chats

edit: Oh, I guess my disdain for TG got the better of me. I assumed with "private" they meant the "secret" chats because it is known that the others aren't "private".

privacy

Telegram will start moderating private chats after CEO’s arrest

StillStackinAfterAllTheseYears

Why? Chats aren't encrypted unless you specify you want to open an encrypted chat