They literally say to store your Recovery keys in a safe place or you could get locked out of your account.

If you don’t know your account password and have lost or otherwise don’t have a trusted device, you need your recovery key to regain access to your Apple Account. If you can’t provide your recovery key, you’ll be locked out of your account permanently.

Print a copy of your recovery key or write it down. Keep your key in a safe place, and consider storing a copy in more than one place. You can also give a copy of your recovery key to a trusted family member.

Don’t store your recovery key in your Apple Passwords app, iCloud Photos, Notes, or iCloud Drive. If you lose access to your Apple Account, you won’t be able to open these apps to find it.

Set up a recovery key for your Apple Account