I got the update earlier today on my iPad Air 2 which was already running the GM version.
13A344 is the version it's now showing after the update. Checked the iPhone 6 Plus which was also on GM version and nothing. I searched the web for others getting the update from GM version, didn't see any results so I checked Twitter and same result, until I checked the forums here.
My iPad mini GM iOS 9 is still the same as well with no updates.