To my understanding, a religious confession could be heard by several people and still be considered confidential (privileged) if they all are present and known by the confessor to be present before the confession is made. If any of those people then revealed any matter of the confession without the confessor's consent to anyone not present, that person would then be breaching confidentiality.
I expect clergy penitent privilege is not intended to benefit clergy or the church but intended to benefit and protect the confidentiality, reputation and public standing of the confessor in matters of religious sin. Lines are blurred due to clergy confidentiality with regards a confession to religious sin vs a confession to having committed a crime.
I expect the courts will eventually be required to rule on and clarify these matters. Perhaps this will become one of the recommendations of the ARC whose recommendations hopefully will be noted and respected by other nations beyond Australia.