EDCE runs on it own desktop on a Mac. If I leave it running there while I switch to a different desktop to get some work done and then go away the display never turns off and the screensaver cuts in after the preset period. But this can mean that the screen saver runs all night when I'd really rather have the display go dark.
This is easily demonstrated by setting display go dark to 1 minute and screensaver activation time to 2 minutes. Then leaving the machine alone with and without EDCE running in its own desktop.