[mulmen]

I think this is because the Mac doesn’t lock at all by default. The actual behavior seems to be “prompt for password after screen saver is interrupted” so that flash is the time it takes the OS to realize the screensaver just turned off and it’s time to ask for the password on the lock screen.

When I leave my Mac I always do a ctrl-shift-eject/power to force the lock immediately.

[gaius]

The saving a screenshot and immediately showing it is a UI trick to make waking up/unlocking look faster, gives the user something to look at while the apps are actually restoring to running state. Just they didn’t think this one through or test it adequately