The Catholic Church has issued a warning to its clergy in Washington state: Any priest who complies with a new law requiring the reporting of child abuse confessions to authorities will be excommunicated.
https://www.newsweek.com/catholic-church-excommunicate-priests-following-new-us-state-law-2069039
The same line of reasoning applies to mental health professionals. But even more so since a judge can order mental health care, but not confession. So why is it considered in one case to keep the avenue open, but not the other?
Well you already pointed at why: because you can be ordered into mental health care. You can’t be ordered into confession, it’s completely voluntary. Furthermore, priests do not have a legal duty of care; they are not registered professionals with professional standards to follow. Their role is defined by the church, not law and regulation.
In a practical sense, such a law isn’t going to work much anyway. It would be almost impossible to prove that a priest had been confessed to, short of someone admitting it directly. So the only way it works is if the child abuser wants to get one over on their priest - giving the child abuser another avenue to hurt someone else.
On the second point, many priests are good people. And they may follow the law simply gecause it exists. So the law could have some impact.