I may be reading too much in to the word "penitent" but presumably it is used by the R.C church, and therefore in Law in many places, to highlight the fact that the one who has sought confession, by that act of seeking, has shown that he is repentant.
J.W org does not make this assumption, it forms a J.C. to establish whether the person truly is a Penitent or not. In that circumstance they could claim anything divulged AFTER the proceedings had decided the person was repentant could be held secret, but the first approach to an Elder, and the decision process by the J.C. surely cannot be deemed as worthy of being kept secret, at those stages they did not know they were dealing with a Penitent.