They're saying that if 432 Hz had special properties, then they'd randomly hit upon it because of the random drift of tuning, and notice that it was better than other tunings; if the keyboardist then came along and insisted on 440 Hz, they'd revolt because it was worse.

But they DON'T revolt, because 432 Hz is no better or worse than 440, 450, 429, 490, or anything else in that range.