Either the documentation is wrong, or this function does not work as expected.

This property holds the current recording audio volume.

This to me suggests volume() and setVolume() control some internal value, but in fact it changes the OS level volume for the current active device, which is not a good workflow, especially if a user has their volume set exactly as they like for other programs.

As I say, I think if this is expected behaviour the documentation needs updating to account for this, if it's not expected then I think the OS volume should be left untouched, with the recording volume set to OS_volume * volume().