"Fragmentation" here is referring to the number of active smartphones on a particular platform running different OS versions. And platform is a proxy for and is being conflated with actual features. iOS 6 will support all actively sold mobile devices and likely be quickly installed. The features, however, will not be available on all devices. That VIP and flagged mail and Offline Reading List won't work on 3GS is peculiar. HTH.
6/13/12 at 1:00pm