Just like other businesses - companies who sell media usually outsource it to different manufacturers.   It might say Fuji on the label for example but that doesn't mean they actually made it.  

To find out who did use Nero.   In SmartStart click on 'Tools' (ToolKit in Nero 6) then CD-DVD Speed.  

Now click on the 'Disc Info' tab.   This will give the actual manufacturer and what speeds your drive supports with this media.   In this pic the actual brand name is also who manufactured it - Sony - one of the few brands that actually make most of their own media.