As you can see on this picture above (source), if 3D is turned off, you can see something that resembles scanlines on the top screen (though those aren't scanlines; for a detailed explanation read the italic text here). Since this can be distracting, especially when you consider that while gaming you repeatedly switch between top screen and bottom screen, I wonder if the current hacking achievements allow to force enable 3D on 2D only areas and 2D only games.