Devices' "volume control" reports do not reflect whether or not volume control works in calls.
https://github.com/ubports/ubuntu-touch/issues/1749 has raised an interesting issue with our compatibility information. Basically every device needs to have its volume controls enabled twice: once for most of the system, media controls, ringtones, etc... and once for in-call audio.
I think we should add another feature listing to make it clear that there is a difference between these two features. This would encourage porters to look into and enable in-call audio volume control more often and inform users who might think that "Volume control" means in-call and out-of-call volume control.