It is likely that the update is not being correctly reflected on the Edge.
Try deleting the following 2 files off the Edge. Then disconnect the Edge from the PC. When the Edge boots up it will rebuild these 2 files. Connect the Edge back to the PC and see what the updater reports.
Delete
Garmin\Device.fit
Garmin\GarminDevice.xml
Can you post the GarminDevice.xml file?
I think what you are seeing is a bug with the web updater. If you use Garmin Express does it offer an update for the Time zone map?