Stereo playback masks differences between loudspeakers with room reflections

Evidence

Naturally there were doubters, and over the years mono vs. stereo tests have been performed. Each time the loudspeaker that won the mono tests also won the stereo tests, but lower rated loudspeakers were given higher ratings. In stereo everything tended to sound better. See Section 4.4 for details. Chapter 5 looks deeper into how we make judgments of sound quality in different circumstances. It concluded that in stereo and multichannel sound recordings include enough reflected sound information about real or synthesized recording environments to confuse the eye/ear perceptual system when all channels are active. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1092

Categorization

• QUESTION: The claim that recording-environment reflected-sound information ‘confuses the eye/ear perceptual system’ — I want the actual mechanism from Chapter 5 unpacked.