This is incorrect, there is no fallback once they have shut you out. The correct answer is to not use a passkey that's managed by the device ecosystem.
Citation? Are you conflating losing access to your iCloud account with a remote-wipe? I’ve used devices which had synced passkeys when iCloud was disabled (MDM gaffe) or unavailable due to a password change, and the credentials which had already been synced continued to work without issue.
