This is based on a string that reads, “Friends can find you by your name, email, or phone number”, and since right now it is more or less phone number-only, we can only assume that support and link to your email account will arrive later on, and presumably it will be the same email account you use for Google.
Unfortunately there’s no release date on when this particular update or change will be arriving, but the sighting of the string in the APK teardown does seem to hint that development of the feature is quite far along, or possibly even ready. Note that Google’s Duo app also had evidence of email account linking last month, so perhaps Google is waiting for both to be ready before launching it. Either way we’ll keep our eyes peeled for more information in the future.
The APK teardown also reveals some other changes, such as the way contacts are shared and also a redesign Group Details page with tabs for shared media and settings.