Google has quietly announced on Google+ that it will be killing off some of the App Indexing features within the Google Search Console.
Specifically, Google is turning off the Fetch As Google for Apps feature to “avoid unnecessary duplication” with what is available within the Firebase help documentation.
Google added Fetch As Google for mobile apps back on May 22, 2015, only a little over two years ago, and is now removing the feature.
A year after Google launched the tool in Google Search Console for mobile apps, Google renamed Google App Indexing to Firebase App Indexing.
Soon enough, I suspect all the features available for those deploying app indexing and using Google Search Console tools will be removed.
Google has been focusing more of their attention on AMP, PWAs, responsive and other technologies over mobile apps within search and Google Search Console.