Pixel 9 Pro, got the update yesterday, same AA prompt and CarPlay icon since.
It does appear that AA support is actually imminent (famous last words). Reading the tea leaves, it looks like
@Bobby's response to me about us for sure getting a similar rectangular interface like CarPlay is correct, since the developers are likely utilizing existing UI building blocks for AA enabelment (the CarPlay prompt in the UI as a clue).
If so, this long and valiant thread is likely not long for the world. In anticipation of this momentous event, we should go ahead and create another "Android Auto complaint Wednesday" thread where we all express our disappointment for the lack of features in the already supported AA weekly every Wednesday