I originally opened a support case on this when I was on version 2.4, which is the version where I first noticed the Device Names and Descriptions were not updating. This was the original response from Support:
I checked with engineering and the metric family and change detection won't update Hostname. Hostname change detection runs in DC for every 24 hours its a separate process. So this would be an enhancement to have one of these automatic processes update the name.
The interesting part was that the DA did show the updated name in the "Host Name" field, but it was not showing in the "Name" field - which is the one that gets synced to Performance Center.
The conclusion from the support ticket was to maintain a discovery profile and run it on a regular basis. So on a weekly basis, I have a script using the API to retrieve all devices, refresh the discovery profile, and execute the discovery profile. I'm up to the latest 2.6 by now and I'm still doing this process, so I'm not sure if this is still an issue.