[keycloak-user] Optional/Alternative in login flows

Hi, I'd like to make a login flow : If the user has TOTP, use it. If the user has no TOTP but SMS, use it instead. If the user has neither use the TOTP normal enrolment to set it up. Setting the SMS execution to optional results in a "missing mobile number" error when I login, rather than skipping the step. Is this a fault in the SMS plugin? Or have I misunderstood the "optional" indicator? (https://github.com/gwallet/keycloak-sms-authenticator) Thanks, Max