For the issue to be fixed, it would first have to be broken. It isn't broken, it just isn't the way you want it. It matches the default settings in the Contexts perspective on the Mac. If you want a Contexts view on the iPad that behaves like the iPhone, take the Mac Contexts perspective, change the view bar to sort by due, save as a new perspective, and sync. Use that perspective instead of the built-in Contexts perspective on the iPad.