Interesting. I can't confirm though - I personally changed my 2FA device 2 weeks ago using a backup code. I couldn't find old yubikey that I used as 2FA for google, decided to regain access with a backup code and add my new yubikey, and it worked flawlessly. It probably helped that I used the same machine as always. Google does a lot of undocumented heuristics in the background, and you either get additional verification or not.