This is what my N9 current does:
0. Set your N9 so it closes on swiping down. (default in PR1.1)
1. Open Music app (which doesn't have landscape mode)
2. Hold the phone in landscape.
3. Now swipe down at its physical orientation. (which should technically be side-swiping the Music app)
4. App closes. (but I didn't swipe from top of the "app"!!)

I'm quite sure it didn't do this before.
Anyways, still confused how it was in PR1.0...