Bluetooth Headphones - Minimum Volume Too Loud

I’ve seen this question submitted elsewhere and the answers simply aren’t enough...

The IPhone’s minimum volume on 3rd-party Bluetooth headphones is simply too loud. I listen to audiobooks with my Bluetooth headphones at night, and I’ve had to use my PC instead of my phone as the source because even at the lowest iPhone volume setting, they are loud enough to hurt my ears. This is not an issue with any other audio source I can connect these headphones to.

What’s doubly frustrating is that you can actually adjust ONE earpiece to a lower-than-minimum volume through the accessibility options, which makes the other earpiece even louder, so I have no doubt that what I’m asking for is possible.

What gives? Why can’t the iPhone present a wider range of volumes for Bluetooth devices?