Plus it's mentioned in the RADIUS RFC that Access-Accept packet from RADIUS may contain a User-Name attribute in which case the access point should "override" (should use from now on) the existing username.
Eg. you have a working MAC authentication, your Ruckus device sends a RADIUS request with aa:bb:cc:dd:ee:ff as username, RADIUS grants access but it also has an attribute User-Name = John Doe. From now on, on your Ruckus access point and in forthcoming accounting packets a user name of "John Doe" will be used.
It's a valid use of the attribute and its mentioned on the page above. However, I can't get this to work - my access points seem to ignore the attribute.