actually i think humans dont see in real 3D.

just make this experiment:
take any tube and place something little inside (around the middle of it or further from you). look in the tube exactly from the front so you see the tube as a circle. now, try to point where is the thing you placed inside on the side of the tube. the longer the tube the more inaccurate you will be. (i tried this with the vacuum cleaner's tube and missed with 4-5 cm)

secondly, think of the 3D movie theaters.

The comment in the description was just light-hearted and yes you are right, as humans all the information we use is detected on the 2D retina, therefore any sense of three dimensions we have is constructed by the brain. The brain is the part that converts the 2D images into a perception of 3D.

With two reference points you can see in 3D. It makes sense that with more reference points, the easier it is to construct a 3D image.