According to Google Webmaster Trends Analyst, Mariya Moeva, talking at SMX East this week, Google is able to gather extra engagement data from apps that use the new API, which helps it determine how useful the app is to its users.
Further announcements by Google at the industry conference include the launch of a new set of documentation for iOS Google app indexing, which works with the new iOS 9 operating system.
Meanwhile, Google Search Console has some beta features App Indexing developers can trial. These include:
App Indexers keen to be a beta tester should visit http://g.co/SearchConsoleTester