I've enabled "Lock screen on resume" in powerdevil and it locks the screen when resuming from anything including suspend to disk and RAM, and when the screen is turned off (e.g. when closing the lid of a laptop). Is it possible to lock the screen only when resuming from suspend and not from the screen turned off?

I close the lid of my laptop to save battery when I don't need to look at the screen (e.g. when playing music off battery) and I was hoping to just open the lid without having to enter a password, though I do want the screen locked when I suspend (to disk or RAM). This behavior can be configured in gnome.

I would suggest opening a feature request at bugs.kde.org

This is possible in 4.6 by writing your own script (my estimate is 10 lines) : catch the resumingFromSuspend dbus signal, and lock the screen by sending the appropriate signal (too lazy to look for it now). And disable locking of the screen when turned off.