I have recently added 2FA for my Google account using an authenticator installed on my mobile phone. After doing this, I have realized that it would be nice to also have the authenticator installed in a backup phone.
However, it was not possible to simply enable another authenticator. The only way was to remove the authenticator and register both authenticators at the same time (scan the same QR code, thus generating the exact same authentication code).
I am wondering if there is any reason for this restriction. I was able to register two authenticators for another application (they generate two different codes, but they are both valid as 2FA).
Is there a security rationale for this restriction or is it just a rather unpleasant UX?