except that the stack you're swiping between is not represented in the layout of the icons - it's on how recently you've used the app.

ie: if i have photos, calender and safari all on the same row of the home screen, and i open photos, go back to the home screen and then open safari, if i swiped left to right (to go backwards) on the bar at the bottom i'd go directly back to photos, not to calender