Message alert sounds in CarPlay ONLY play/sound when using Waze (bug or integration)?

There's been a lot of talk lately, including by me, that Messages Alert Sounds do NOT play with CarPlay! Some say it's an Apple safety feature, others have tried to find integrate reasons why yes/no sound is played when a message arrives.

We recently visited our BMW dealer and while experimenting with their on-site Genius found that Message alert sounds WILL be heard when CarPlay is active AND when you are using Waze! It definitely happens when Waze is active (navigating)... not certain yet if it will work if Waze is simply running in the background.

Here's the second strange part though: On my wife's phone, Waze will launch automatically whenever she connects to CarPlay. My phone for some reason does NOT automatically launch Waze. So she gets into her car, her phone connects to CarPlay, and she DOES hear alert sounds from Messages. I get in and connect to CarPlay, Waze does NOT connect automatically, and I do NOT hear alert sounds from Messages... even if I launch Waze afterward!

Anyone else have this experience?

Is it really an "integration" that Apple has made with Waze?

Is it some kind of Bug (or am I missing a setting) which allows my wife's phone to play message sounds (but only when Waze is running) and my phone does not?

Car: 2018 BMW x3 with CarPlay.

Phones: iPhone Xr, iPhone 12Pro (we just upgraded), all running latest iOS 14.6.

Thanks!!