We got another way to show the MAC address.
Since NetSight resolve the OUI in the following file:
usr/local/Extreme_Networks/NetSight/appdata/System/definitions/oui.txt
Clear the oui.txt file, and restart the NetSight Service.
NetSight has no data to resolve the vendor code in oui.txt, so it shows the full MAC than OUI.
But this will destroy all the OUI format,
backup the oui.txt before you do it!
You should contact the Global Technical Assistance Center (GTAC) and open a new problem ticket for this issue.
The experts should be able to tell whether this is a bug or working as designed.