At this point I'm just guessing, but I wonder if it's not an issue with the Body Control Module.
My SEL has the "OFF" switch shown in my picture above and the lights operate as you describe when it's selected to off (dash lights, footwell/ambient lights only). When it's selected to on, the dome light comes on every time the door is opened or the keyfob is used to unlock the door. I also tried on our 9/2011 build SE, and when they're set to on they operate the same.
At this point you've done all the things that could be reasonably expected of you, so it might be time to let the dealer take a crack at it.
Sorry I couldn't be more help.