When a Part is reclassified, the attribute values from earlier classifications remain on the part and can be viewed by modifying the layout for the Part type in Type and Attribute Management to add the allNonSchemaNonClassificationMinusClassificationIbas dynamic attribute list. It is Windchill standard behavior to preserve attribute values on an object after the attribute has been removed from the schema definition. These attributes, which are then considered “non schema attributes,” contain historical information and as such Windchill does not delete these values. In order to prevent these values from being passed to downstream ERP systems, they should be removed by editing the Part through the Windchill UI during reclassification.
The above PTC R&D behavior makes it very easy for users to unknowingly send erroneous data to ERP systems. Without knowing to review and nullify relevant attribute values, the user using the simplest path to their goal would not remove irrelevant attribute values, and they could then pass to ERP from reclassified Parts. Historical data would be retained in the object history for forensic purposes, so that should not be used to justify this behavior. The offered solution requires the modification of the layout and education of the end users instead of systematic handling of the common use case.
I would suggest reviewing the decision to implement this behavior to cater for user simplicity.