As @regecks says below, you only need to add it temporarily and then delete the app. I agree they need the ability to have multiple keys. I personally think th

As @regecks says below, you only need to add it temporarily and then delete the app. I agree they need the ability to have multiple keys. I personally think the reason they require both to set up a security key is a user recovery issue. TOTP is highly reproducible and a security key is not. You can't back up your private key (by design). You just have to buy several and store them separately. I can encrypt my seed, put it in a QR code, and print as many copies as I want at no cost. If my backup Yubikey fails, I'm toast if I need recovery.