My best guess is that Rhino is not firing the "environment changed" event. If the event was being fired, the Octane plugin would be reloading the Rhino environment.Couldn't the Rhino-reload-event be used to trigger Octane reload of the env map?
I think doing this would be incompatible with the HDRLS Rhino connection. I have implemented the live connection to HDR Light Studio in a number of other Octane plugins, but that will not work when the HDRLS Rhino connection is made available - since it uses a difference method to provide the HDR map (a bitmap rather than a file) - so I'd rather stick with the method recommended by McNeel than implement a hack - sorry.VfR in RT mode is using the live connection where a new HDRI file written at a temporary directory. A support of this would be the best way. But if it's no easy done, than I understand your restraint.
Paul