Application security settings 'Clear entered master password'

Jul 1 at 8:44 PM
Hello,

I have trouble understanding the Application Security setting 'Clear entered master password'.
It is explained that leaving the screen without unlocking the database will clear the entered master password.
However if I am on the QuickUnlock screen and I don't enter the last 3 characters and leave the screen, the next time I launch the application, the QuickUnlock is still functional (so the master password is still cached somewhere).
Can someone explain what this option really do ?

Thanks