Lenny Lipton states that...

"As humans, we have two eyes. Not just because we need a backup eye (though it can be useful), but because each eye sees the world in a subtly different way. The combination of the two slightly different perspectives forms a "stereoscopic three-dimensional" image. "

Therefore the concept of stereo-immersive uses the stereo viewing illusion to trick the viewers mind into thinking he/she is inside the illusion.