Not sure of the old covenant concept of forgiveness, but could this have something to do with simply raising the virtue of forgiveness to it's proper place? It is HUGE! It is incredibly important. Just as he did with lust, hate, etc. It is HUGE. . .much bigger of a deal than you think.
Yes ... it is HUGE! As Ed Sullivan (you young kids may not remember the Ed Sullivan Show) used to say, "Tonight, I have a really big shew (that's how he pronounced "show") for you!"
The Pharisees felt justified in condemning Jesus (among other things) for the AUDACITY he had in telling people that they were forgiven!! They rightly questioned, "Who can forgive sin but God alone?". Oh, they thought they had him between a rock and a hard place ... literally, it seems, in the end!!
They were, of course, totally unaware of the "visitation of God" going on in their midst.