I guess technically this makes hearing in one ear a "zero dimensional" sense -- all you hear is a presence or absence of varying intensity with no "position" data -- and stereo sound is "1D"

I.e. all you have is two eardrums that let you judge how far a sound source is to the right or left of you by whether it's louder in your right or left ear

The other two dimensions of "3D audio", front/back and up/down, are illusory information your brain calculates via deduction, based on your personal HRTF -- clever little hacks based on stuff like the shell shape of your outer ear causing subtle changes in high treble frequencies depending on exactly where a sound is coming from (treble sounds coming from behind you get blocked while ones coming from in front get amplified) and making little judgments based on subtle 3D movements and rotations of your head

Which is the whole reason binaural audio works even though it's just recorded with two mics and played with two speakers in your headphones, and why it's so much more instantly convincing when it includes head tracking the way AirPods do

It's also why, even though your ability to hear positional sound is very convincing to the brain, it cannot be relied on without vision backing it up and why the game of "Marco Polo" is surprisingly difficult