iPhone bluetooth volume limiter

iPhone music volume through Bluetooth car stereo connection is literally half (probably even less than half) volume of FM Stereo, CD, Satellite radio. I can turn the volume on both the phone and the car stereo to 100% and still have a quiet conversation with someone inside the vehicle with the road noise from the tires actually being louder than the music. I've experienced this problem across numerous different vehicle stereos and with different iPhones. I've tried every fix I could find online and none of them work. This is *DEFINITELY* a well known and extremely frustrating bugaboo of the iPhone itself, not anything else. I just received my brand new out of the box iPhone 11Pro Max and same thing as all my previous iPhones, of which I've had about 5 now.

Any new data out there on this?

Thanks, you guys rock and iPhone is still the coolest thing in the world.