It occurred to me after the last post on the confusing gesture shortcut to switch apps on the iPad that there's another potential issue at play. Going backwards through your app history means moving from left to right. This is the reverse of what happens in a web browser, where navigating backwards goes from right to left.
It seems inconsistent that ordering by time goes in one direction in Safari and in the other direction system-wide, especially when similar swipe gestures can be used for both. Maybe these two models need to be reconciled.