Thanks for letting us know your findings, hopefully it will help some US Sync Users.
Unfortunately, in the UK things work differently. The option to update over Wifi is present, but will not work.
I now have 2.3 installed by the dealer and have tried 3.0 myself in the past. None of these have fixed my issue, mostly because it's HARDWARE as proven by diagnostics checks.
In the past I also had AA vanish from the menu screen, but a Factory reset brings it back as an option without the need to change to a new firmware version.
For clarity, Android Auto does load up on my Sync 3, but without warning and for no reason it simply fails and reverts back to the main menu. The video I posted above clarifies what I am trying to explain.