Are you sure you're getting FC on flights that aren't "domestic" segments operated by DL? AFAIK DL miles cannot be used for any partner award tickets in FC, although if GOL isn't a full member of SkyTeam, there might possibly be an exception. However, my guess is that you're looking at business class award tickets regardless of the routing and who operates the actual flights. [Note that "Delta One" is a business class product despite it's new name as the updated version of DL BE service.]