In other words, both Kinects were connected when I took that screenshot of Device Manager.

Do you mean you cannot locate the second Kinect for Windows Camera in the Devices By Connection view?
Here is a little trick. Find and select the device in the usual Devices By Type view, then switch to the Devices By Connection view. The tree nodes will be automatically open to show the selected device.
Specifically, select first camera, switch view, get hub props, switch view back, select second camera, switch view, get another hub props.