The fact that you say "2D perspective", proves you still don't understand how it works. As I say above, any image can be displayed in 3D.
Mush isn't talking about making a 2d screen show a 3d image. He's talking about how do you make a 2d game which has NO perspective 3d. It doesn't make sense.
You're asking me this question, aren't you a designer :?. I'm sure I saw a thread the other day which suggested you are. If he had bothered to watch the video before posting he'd know that the 3DS uses a parallax barrier technology. It all works very simply, you make sprites and objects on the foreground plane appear as if they're floating, by displaying background and foreground objects at independent speeds using the parallax barrier. Pushing the 3D slider up on the 3DS increases the rate at which the foreground pixels minutely vibrate, while all background pixels are made to display at a lower rate. The discrepancy between the two fools the brain into thinking all the foreground pixels are floating.