Update: Here the official answer from Symantec's Brian Foster:
"3.2.1 is the latest shipping English version of NDD. 3.2.3 is the current version number of the Japanese vesion of NUM. 3.2.3 only included changes made for support of the double byte character set. There will be a patcher available for the Japanese version of NDD when MacOS 7.6 ships in Japanese (~end of Feb.)
If you are receiving reports that indicate that there are US customers with non-localized versions of 3.2.3, please have them contact our support department."