I had it done yesterday as my car was already at SC. Two pieces of info:
1) Fob has worked flawlessly since I got it yesterday, but waiting to see. It also worked fine for first week after delivery. It is a firmware update per the service doc I received post service.
2) Must be done at an SC. I was told this at SC and they explained it’s not a matter of IF mobile can do it - they could take the device used to update firmware anywhere. However, as release notes say, they’re super sensitive to security. If one of the update devices were lost, it could impact fob security for many cars. If you live 200+ miles from an SC, not sure what plan will be. But you can not have them do it via mobile just for convenience.