It's hard to encrypt "all". "End to end" encrypted would mean that a message is encrypted while in transit. "At rest" encryption would mean that the plain text

It's hard to encrypt "all". "End to end" encrypted would mean that a message is encrypted while in transit. "At rest" encryption would mean that the plain text message is not saved on storage, just the cypher. Software however can behave in a way that all of these are true, yet, the plain text is readable by a third party. For example, the app can send the plain text after you decrypted it. Or the encryption could have multiple keys that can decrypt; you can have a private key for yourself, and the authorities could have a master private key that decrypts all. Your phone could have a middleman between the touchscreen and the application, and so, your "keystrokes" can be stored and sent somewhere, for example, by your keyboard application.