That is the point, RDan.
Stereo mixes rely on reverb to try and simulate "space" and "openness".
It is well known in recording to record in stereo (with two mics) in various configurations including binaural recording with microphones inside a dummy head, dummy ears, etc.
The other prime point of my post is that there should be and there is a difference (quite significant) when you listen to stereo mixes on phones.
Usually recently some headphone manufacturers have adopted some Dolby Atmos or whatever it is called to simulate binaural virtual environment. That is something of necessity for Virtual Reality gaming and experience.
Ambisonic is a step into great number of microphones >2 (which would be stereo or binaural). Usually 4 mics in a tetrahedron configuration pointing "away" from each other (Ambeo Mic by Sennheiser whic costss £1500). Then this 4-ambisonic (also know as B-format) usually gets "mixed" (decoded) into either 4.1 (for loud speakers + subwoofer) or binaural (normal headphones).
It is not just about reverb and simulated multiple-reflections.
Quite similar to surround mixing but for headphones.
There are even some headphones with multiple speaker-drivers inside each of the channels (Left, Right), which is insane and overdoing things.
I wonder if reaper has such plugins for binaural, like it has for surround?!
At the moment I am using:
Ambeo Orbit (free):
Ambeo Orbit
FreeAudio 3DAudio (not free):
3DAudio
dearVR 3D (very expensive and crashes Reaper for some reason, so I had to return it):
dearVR 3D