That's true, though the swipe is from up to bottom -- the other swipe just puts application into a recents view. Felipe (now famous for his arguing with Elop) wrote a patch and me and Urho drove it through the management at last. Congratulations to Urho and Felipe on persisting and getting it not only as configuration option but also in Settings UI. There are so many small details to consider when introducing such "seemingly innoncent" features that it was not so easy to convince people. Still, it shows it what is possible to achieve together in an open collaboration mode.
Yes, there is a setting to activate a swipe down gesture that will close the app directly. You start the swipe from the top of the display, move your finger down till the end (or so) and you see the window following your finger down, disappearing through the bottom of the display and being effectively closed. Very intuitive as well.