Question Cannot access 60fps from 60fps Brio Webcam

I have a Logitech Brio webcam that can provide 60fps 1920x1080 as proven by use with OBS and Logitech Capture software.
Unity WebCamTexture however can only see the camera as though its maximum frame rate is 30fps even when 60fps is requested.

Code (CSharp):

1. webcamTexture = new WebCamTexture(webcamDevice.name, 1920, 1080, 60);
2. webcamTexture.requestedFPS = 60; // Attempt 60 if available
3. webcamTexture.Play();

If I connect Unity to a 60fps Virtual Webcam created by OBS or Logitech Capture from the same Brio camera, Unity works fine at 60fps - proving that Unity is setup correctly and the hardware pipeline is correct.
I've tested some Unity OpenCV and AVPro implementations and they appear to suffer the same problem.
Apart from spending a great deal of time implementing my own C++ DLL that wraps Windows MediaCapture or equivalent can anyone suggest a way to get 60fps from this camera without having to run virtual webcam streaming software?