I don't know anything about the car's sound system, but aptX is a pretty common Bluetooth audio codec for music and these days it can run up to 420kbit/s with the adaptive codec, or 576kbit/s with HD, 24 bit at 44.1-96kHZ, so it's not unreasonable to think you could hear the difference between high and low quality audio sources with that (since even high quality compressed audio tends to be less than 420kbit/s)
What has been heard cannot be unheard. Back in the day I did some ABX comparisons of various mp3 encoders. I unwillingly trained my hearing to spot encoder artifacts forever. I tested encoders more than 15 years ago. I still hear mp3 compression without trying. Bluetooth SBC codec is even worse. Wish I could turn this off but I can't.
It’s hard to tell if it’s just HN imaginary “horrible sounding” or if the mic is on for some reason which makes it actually sound that bad.