I too don’t want to get into a discussion about Bluetooth, but I can say I had always connected Android Auto with Bluetooth. I didn’t mention you “usually” needed to connect the phone with a USB the first time AA was started but once connected the USB could be disconnected. I am aware Apple Carplay always required a USB connection. I will say, I was never happy with the AA connected either way. It was very temperamental and I attributed that to the conversion process when adding the 8" screen to my truck.
Without spending a lot of time I quickly found this youtube referring to this. Go to the 2:10 mark in the video. The guy makes reference to this but doesn’t really explain it in depth.
There are numerous other videos that explain how to connect wirelessly. Believe me, I appreciate very much your expertise on this system and the help and support you provide. My intention is simply to help others not to prove how much I know about this subject. which is very little.