GM parts-bin engineering (pre-bankruptcy, maybe better now). The tilt/slide buttons on my sunroof have no markings, took me forever to remember which was which, was always thinking "how can they not put any markings on the buttons, no words, no symbols, nothing". Then one day after I had the car for a few years I was climbing around trying to see the connector on the back of the rear-view mirror, so I had the back of my head up against the windshield, looking towards the back of the car--lo and behold! The buttons are marked! It's just that the panel is tilted away from the driver and the markings are facing out the windshield, so the only way you can see them is if you're clinging to the hood like the Terminator, no way from the driver's seat!
I can only guess is the buttons or panel were from another application and they said "close enough".