In the Boundaries and Relationships section of Device it says:

The DeviceMetric models the properties of the Observations generated by the device, such as whether or not the Observation is a setting.

We should clarify whether DeviceMetric can model properties of Observations about a device, but not generated by the Device.

As a use case, consider that the adjustable height of a crutch would be defined by a DeviceMetric, but the crutch itself would not report the current height; instead that might be reported by e.g., a Practitioner.

If it is intended that DeviceMetric should only be used for Observations reported by the device, then we should add language to both Device and DeviceMetric to indicate that, and that the device must also be a "communicating" device (whether the communicating category is indicated or not).