I believe AA was available via a hack (AIO Tweaks or something like that). You would put the hacked firmware onto a USB drive, then plug the drive into the arm rest port and flash the new firmware, and you'd be able to get AA. I don't know the details, but I believe that on the 17/18 model years, you were no longer able to update firmware via the USB port in the arm rest. That's why there were a few threads that popped up about accessing the CMU, these were people who were trying to figure out how to upgrade the firmware on their own so that they could install AIO Tweaks.
So CX-9s that had AA before it was officially released by Mazda, were all unoffical, "hacked" versions of firmware that they had installed themselves.