Comment 10 for bug 36568

Sorry - I forgot to mention, Nicolo, that you will need to uncheck the box in Gnome-Screensaver saying 'activate the screensaver when session is idle' or you will have the screensaver on for 29 minutes of your AC time!

Because, as you say, you can't have both the screensaver disabled and the 'lock on screensaver' option on, you are correct that there is now no way to make the screen lock when blanking, so perhaps you should file a bug.