The brain can judge distance from sound specifically its reflections, speakers close to a wall create reflections very close in the time domain to the original sound this means your brain ’knows’ this is a small space. Speakers further in the room have a longer delay thus the brain hears a bigger space.
This. It’s all acoustics - treble/staging is very dependent on how pure the initial sound wave is when it hits your ears. Further from the wall, the back reflection is sufficiently delayed that your ears/brain can distinguish. Too close together (too close to wall), you can think it’s just "muddying" the wave.
I believe most know about the lower frequencies being less directional and therefore less depending on room placement (think sub anywhere in the room). For these less directional bass frequencies, room modes are more the driving factor (frequency response, or "boominess" vs "suck outs").
...and maybe look for another dealer (or at least confront the rep [who hopefully isn't the owner])... :-)