If digital tags are found to be assigned to inappropriate digital state sets, changing the state set does not change historical data since the state set is also held in each archive record header. To correct the historical data, you have to offline-reprocess all the archives.
If the PI Server could be set, either system-wide or tag-by-tag, to always use the latest assigned digital state set when retrieving values for the tag, this would completely remove the need for such reprocessing.