The dial control design is quite nice. The only (and critical) problem is that the target for controlling the volume is — Staff replied: “The single finger gesture has a "normal" hit region size. If it were a large button, that's about the size of it if you could see it outlined there.”
The dial control design is quite nice. The only (and critical) problem is that the target for controlling the volume is miniscule. One needs to tap and hold precisely at the current volume location to make adjustments. Needless to say, this is impossible to do without looking down at the device. (see attachment)

The simple fix would be to allow sliding a finger up of down anywhere on the dial to control the volume.