I'm pretty sure you have to turn it over completely to shut it off, not on it's side. I've never tried it though.
It used to work as demonstrated in several videos on YT,
However according dji tech support (very hard to communicate with unless you're fluent in Chinese) it doesn't stop unless spark is turned completly upside down. I wonder if a recent firmware update changed the turnoff tilt from 90 to 180 degrees? if so I wish they'd warned us before we risked losing fingers. I thought for sure I'd lost a couple of props after I dropped it in the gravel. It kicked a few stones around while squirming on it's back before finally shutting down.