If this is true, then why does the priest hearing the confession, then assign tasks that must be done (such as: say 20 Hail Marys and $20 in the collection box) in addition to Christ's forgiveness through Grace? If Christ's death on the cross is sufficient, why are the additional tasks necessary or warranted?
It seems to me that your Jesuit Priest is inferring that the church, because it is not perfect, can demand punishment (or whatever it wants to call it). If the church is demanding this "punishment" in order that the sinner be allowed to remain a member of the church, then either the church does not truly believe that Christ's death on the cross is sufficient for Grace, or (could it be) that the church sees an opportunity to (and I will put it quit bluntly) "blackmail" the sinner by saying that we cannot allow you to remain a member unless you do this and this and this for us.