Apple has removed App Slicing, an iOS 9 feature that allows apps to download only those assets that they need to work on a target device. The company said the feature would be reenabled at some point.
App Slicing means app downloads can be smaller, which is good for developers and users alike. Without App Slicing, apps must be universal downloads that will work on every device. For a Hybrid app designed for iPhones and iPads, images for designed for an iPad Air are included in apps downloaded to an iPhone 5. It's wasteful in terms of both storage and bandwidth used to download.
Apple introduced App Slicing for iOS 9 during its World Wide Developer Conference in June of 2015, where it was applauded and cheered by developers on hand for the event. On Thursday, Apple announced it was disabling the feature for now.
App Slicing Illustrated by Apple
App slicing is currently unavailable for iOS 9 apps due to an issue affecting iCloud backups created from iOS 9 where some apps from the App Store would only restore to the same model of iOS device.
When a customer downloads your iOS 9 app, they will get the Universal version of your app, rather than the variant specific for their device type. TestFlight will continue to deliver variants for your internal testers. App slicing will be reenabled with a future software update. No action is needed by you at this time.
Ars Technica reported that the move was related to a problem related to restoring new devices from backups of older devices.