There is another way, but you can't keep it open forever. Any app can request to stay open for a short time to do anything it wants after close. I use this for an app that saves data to the cloud. No reason to make the user wait around for the save. You can't stay open forever though which I suspect is what they were doing.
Just wanting to point out there is a third option, though not indefinitely.
Just wanting to point out there is a third option, though not indefinitely.