Disagree - I want to be able to have my phone "casually" locked (when it's on) and "securely" locked (when it's off). If the casual lock is harder to break, that's icing on the cake, but the important thing is that I can quickly prevent access to the phone, and that it will revert to that state automatically after some time.

Ideally my phone would go into "secure" locking mode (requiring my 7 word passphrase) after not being unlocked "casually" for more than X hours.