If I understand correctly, you used to have a template of the Casework category, made in a previous version of Revit, which you had been able to edit to remove the Finish parameter. What happens when you open the same old template in 2013?
Open old template in 2013 - The 'Finish' parameter is automatically created as a TEXT parameter.
Any EXISITING parameter named 'Finish' (INCLUDING Shared Parameters!) is automatically RENAMED to 'FINISH1'. Of course this breaks Shared Parameters and mayhem ensues.
Any attempt to insert a FAMILY created in previous versions with the 'Finish' parameter removed results in the 'Finish' Parameter being added.
Any attempt to insert a FAMILY with an existing parameter called 'Finish' that is NOT a TEXT field results in a failed insert - 'Cannot create parameter - load cancelled' or error message to that effect.
I have since unpacked the RTF/RFA format to see if the structure was something simple like XML that I could tweak, but no, it's some form of encoding, and I don't have access to disassembly tools here! The file format is interesting however, and does contain some form of XML / text fileds which give me some clues as to how people are writing apps that find things like Revit Version Numbers from families. I notice that all the templates that ship OOTB with Revit 2013 still claim to be made by the BETA vesrion in February 2012 by the way...
Why some of this data could not be exposed in a 'MANAGER'S MODE' of Revit is a bit beyond me, and yes I am aware of the older versions debug mode - it would make some of the aspects of managing a BIM system MUCH easier! Perhaps a command-line switch to activate 'BIM MANAGER / CAT HERDER MODE'?