We know that down the line a confession will be shared with others, this reference seems to indicate that in order to keep the privilege they must remain secret.
And what is the legal meaning of that? The State Court determines on a case by case basis whether or not any challenged church communication meets the legal standard for confidentiality under the related STATE LAW. The California case that you cite was adjudicated under the laws of California and not under Federal Law.
STATE LAW vs The US Supreme Court however has not decided on Elder/ JW communication confidentiality as not being secret -or more importantly, not protected under the constitution or federal law because of the manner JW handles judicial cases (aka clergy/ penitent) does not comply with a LEGAL standard.