Since the first MIUI 12 to Mi 9 Lite, the AI preloading doesn't work, I recorded my screen to show better what happens when enable, just after the system disable it.
Strange, but it really worked doing it that way. When I was on MIUI 11 the on / off button worked normally, so it didn't occur to me to press the text. Thank you.
Everything in the "MIUI lab" screen is experimental, not a "must". You may disable it if you worry about battery life. As for how it works, I doubt anyone had studied it, even we don't know.