Mom's Prius vehemently complains when the key is not in the car.
I haven't ever tried to idle it without anybody in the car.
My guess this issue is about a feature of remote start/warm-up that some cars were supposed to have a few years ago. Remotely start the car from in the living room, and have it all nice and toasty by the time you get to the garage.
In fact, there could be a risk that one properly parked and shut off the car, then accidentally bumped the button.
Kind of like the infamous butt-dial on cell phones.
It should be easy enough to add a 15 minute idle shutoff feature on the cars.