When I was checking a password, the screen turned off on my phone. When I turned it back on, the screen previously shown was shown briefly before the lock screen animation played. The password itself was visible until the lock screen animation completed. Once the lock screen was dismissed with the PIN, the password went back to obscured with a "Reveal" button.
1password should hide the passwords on the screen when the screen turns off, so that when it turns back on the password is not shown before the lock animation plays. Or, better, the lock animation should simply be skipped under these circumstances to prevent leakage of less sensitive data (logins, etc.)