They did not allow press to take images of the device when the display was on.
They knew images couldn't capture the 3D so they did what this company is doing and used a bunch of vague renderings to try to express how the thing worked.
Since it's probably the same underlying parallax tech powering both, I'd guess the reasonings are the same.
It's not. Looking Glass is an advanced version of lenticular optics, which is 100+ year old technology, except used to create a multiscopic display(many views).
Nintendo 3DS is newer technology, known as parallax barrier. However, 3DS is only two views, which is pretty much only useful for a single viewer.
The later "New 3DS" introduced a face tracker that made the effect work continuously across most of the LCD's viewing angle for a single viewer.
Curious why they didnt go for a similar setup here? Though the looking glass display allows for multiple viewers.