They don't do a 3d model, but it is a real stereo image. There's a bit more info in their docs: https://developers.google.com/vr/concepts/cardboard-camera-v...
Until you look down. Or until you have a different eye distance than average. Or you try to move a bit and there are things close enough to make you dizzy.
Cardboard didn't need any of those fancy things, of course. It was bad enough with abysmal latency.