Some are quick to promote apps as being safe for your use just because they are encrypted. I will talk about how many of the popular apps that are commonly t...
And this is not a theoretical threat either, something like that was done to identify democratic activists during the recent Hong-Kong protests and put them in jail.
Source?
https://www.zdnet.com/article/hong-kong-protesters-warn-of-telegram-feature-that-can-disclose-their-identities/
Note that while this is about Telegram, this problem of reverse phone-number lookup also exists AFAIK with Signal.