Hmmm? Non sequitur.
The inability to measure something does not equate to it being an illusion. Old joke about bad science: “Why are you looking for your lost keys under this street light when you dropped them way down the road?” “There is light here and it’s too dark to see anything where I dropped them.”
Illusions are rather aggressively studied, and they map human perceptual realities (biology + psychology) onto physical systems. Some illusions can be fully explained while others present challenges. Even still, if a playback system involves illusions the effect is real (primary) and any deficient measurements that may be available are irrelevant.
Consider the Shepard Tone:
Etc.