Absolute Bluetooth volume control is on by default. To disable Android absolute Bluetooth volume control, users can go to Settings > System > Developer options and select the toggle for Disable absolute volume.
The source Android device can also register volume notifications via Bluetooth. When volume changes are made with controls on the sink, the sink sends a notification to the source. This lets the source accurately display volume information on a user interface.
Another issue might be low volume which can also be result of Bluetooth absolute volume setting, which you should try disable if you’re experiencing such issues. In some cases they’re controlled separately it’s possible to get a louder volume level than if the Bluetooth system volume was being controlled with the headphones. With it disabled you can have headphones volume on 10 and media volume maxed out as well.
But generally all those settings would still require you to disable Android absolute Bluetooth volume on most of devices.