backbutton does not minimize app

I was always wondering why backbutton handling was not well supported on windows-phone platform until windows@4.2.0 was released with backbutton support CB-8481.

But currently this fix became a real problem for me since I tried to release a new version of my application to the windows store. My application was not approved by ms team, because it was not suspended when there is no history. So I had to downgrade to windows@4.1.0 to get an approved application...