FIDO2/WebAuthn relies on public key technology - so does also have a secret key - but is designed to be kept secret from the service/server one authenticates against.
For use - FIDO2 is more like a multi-use id. Like a driver's license many services accept as id. If you lose it - you don't restore a backup copy from a safe - you use your passport until you get a new one issued.
This makes more sense than with TOTP as the services only need your public key(id) on file.
