Could humans theoretically see infrared better than regular light?
No, retina doesn't have or has too few infrared receptors.

Practical example: most remote controls use IR LEDs (infra red light emitting diodes) to send commands to a receiver device. So take a remote control, keep pressing a button and look at its front. Do you see any flashing light? Now take a camera (phone camera, photo camera or video camcorder) and look with it at the remote while pressing a button. Now you see it producing white light. The camera sensor detects IR. That is how night vision in cameras work.

What you read in that article is about how light is reflected by the eye (the pupil). There is nothing to do with the retina which is on the 'back wall' of the eye ball.