Sorry, but that’s not true. While technically true, that full disk encryption doesn’t exist anymore, they use file based encryption which, functionally, is the same thing. Source: https://www.androidauthority.com/how-to-encrypt-android-device-326700/

Pretty much my thoughts, yes.

In order for the FDE to have any usefulness, the key has to be derived from a secret that only the user of phone knows (I.e. a secret PIN, password or pattern)

I think the main reason people still prefer Discord over Matrix is the fact that everyone is on discord but very few people are on matrix (at least, non-tech people).

If your entire family uses Discord, your friends use Discord, your classmates use Discord, at some point you will have to use Discord too.

And if you’re forced to use Discord, then why also have a Matrix account too? That’s a bit redundant when you think about it