Which only worked if you had both phones working at the same time... I'd bet a sizable portion of new phone enablements are due to losing the previous phone irrevocably.
Also, as of last week, there existed an issue with special characters when trying to import and the app would just freeze or not recognize the QR code pattern at all, so you better had backups of all your secret keys.
Both issues made me switch to Aegis and appreciate my past self backing up the secrets with KeePassXC.
For me, I'd usually be on the desktop when setting up 2FA anyway, so I'd just save the QR code from the desktop browser ("Save image as ..."). When I needed to set up a new phone, I'd open the saved image on the desktop and point my phone at the screen.
Screenshot -> Print is one backup method.
Screenshot -> Encrypt -> Save to secure location is another method.