I imagine if you had enough realtime keystroke data, you could even identify a user using nothing more than how they type on a keyboard. That's some scary stuff.
Privacy advocates would better serve the public if they instead educated people on how to communicate securely instead of producing yet another black box that users can blindly put their trust in. I suppose this is better than nothing when dealing with less capable actors, but for those who plan their future years ahead, doing something on this phone, only to have it bulk collected and stuck in a database for decryption and analysis later when it serves the political will of those in power is counter productive.