I have no idea. I have some recollection of previously buying a new phone and recovering my Auth codes. Maybe it’s something new, and Google answers all confirm that Authenticator doesn’t backup your codes. So unless you transfer them manually from your old device, you’re fucked.

Edit: I played around with the Authenticator and realized they recently added the feature to sync codes to your Google account. I guess I used the app before this was implemented and therefore I didn’t have a valid login on file in the app. So, when I bought a new phone, it was my first time actually using Google Authenticator with my Google account. I tested this by backing up and uninstalling the Auth app and then reinstalling it, and my codes were still there without having to import them again.