Pitch switches to the higher frequency only when spacing is nearly perfect

Evidence

To the author, both pitches are apparent at 5.5 (0.015277 x 2π radians) degrees offset, and the 300 Hz pitch becomes perhaps slightly dominant at 5.75 degrees. That is, not until the holes are almost perfectly evenly spaced does the pitch finally start to switch to the higher frequency. — Eric J. Heller, Why You Hear What You Hear- An…, 2104

Categorization

• QUESTION: Why is the perceptual system so conservative, sticking with the lower pitch until spacing is near-perfect? Possible evolutionary bias toward lower pitches?