The only thing I've noticed with AA (on my Google Pixel) is that once you connect the phone you need to go and "open" AA through the main screen. You can then proceed to go back to the Chevy/GMC screens. If you don't do this the text messages will only come through the Truck and not Android Auto (until you launch it for the first time). Crank up AA and say read me my text messages and there aren't any to read if it hasn't been started before.
2017 GMC Canyon SLT V6 2WD Crew Cab Short Box