The "readme.pdf" file that refers to ver 6.2 of the DNG Converter contains the following statement:
This version of the DNG Converter is now provided with an installation utility. The installation utility is designed to place the DNG Converter application in the Application (Mac) or Programs (Win) directory and install a set of color profiles required for the DNG Converter to function properly (emphasis mine). These profiles are copied to a common resource location.
Does anyone read this to suggest that older raw (nef) files that were converted with earlier versions of the software should be (or may benefit from) reprocessing with this latest version?