Pixels were just ranked higher in several tests recently due to the Titan chip. Doesn't mean third party apps are secure (as we all know Apple is far more tight about app security in the AppStore than Google), but the phone itself, stored biometrics, etc, are very secure with Titan. It's actually the same cryptographic chip Google uses in their public cloud servers (just scaled down).
As for the OP, I've had this same issue for a couple years now, regardless of what version of AA, Sync, Android, etc. The fix in general is to set the Bluetooth phone settings to use the phone ringtone. This only seems to work sometimes, and it makes no sense as AA is wired, but there is a conflict between AA and Sync on all versions. It seems to work sometimes for me when I change this setting. But be forewarned, new updates seem to overwrite the setting. Here's a video showing how to change the setting.
How to Change the Alert Tone in my Ford F-150 - YouTube