Turning monitor off bypasses locked screen.

When you lock the screen and then turn off your monitor, the keyboard will function allowing you to open applications, type into applications, etc. without the locked screen requesting the password. Once you do that, you turn on your monitor, you press any key on the keyboard to get the password prompt, and once you put in your password you will see what you have opened or typed in an open application.

The easiest way to see this is leaving a terminal application open before locking the screen.