If its a problem, its quite widespread. I'd think its a software issue and anyone not experiencing it just unplugs before the car goes to sleep. Sometimes the car can stay awake for hours after charging stops.I don't believe this is normal behavior. It never was, and the manual doesn't say that it is.
The only people I know with M3's got them recently, but they all do the same thing. All I need to do to be able to unlock it with the button is open the app and have it wake the car. I don't need to press anything on the app, it just needs to be woken up. And It does say waking up and take a few seconds every time. But the presence of the phone makes no difference.