App Indexing & App Links & Universal Links
I'm confusing App Indexing & App Links & Universal Links.
App Indexing enables you to show app deep links in a google search result.
As long as your app has deep links (even though you use custom URL scheme), you can see deep links for the app in a google search result.
App Links & Universal Links enable you to let user open your app instead of web pages when user access your web pages.