I don't know why the reason should matter? In this case, the catalog name changed, in the effort to create standardized naming conventions. Does that make a difference on whether I can purge a catalog reference or not?
This will only work on specs that you have created.
You can use WinRAR to open the pspx file. Inside you'll find a folder called "editor".
In the editor folder, there is an .xml file, "CatalogReferences.xml"
This xml file contains the path for the Catalogs that are associated with the spec. You can change the Catalog name in the xml file.
Make sure you open the xml file from the WinRAR aaplication and when saving, it saves back to the archive.
Hope this helps.