I did not know that... Maybe it's openCL exposing both devices. /me goes read up on the mux driver...In OSX Apple actually uses a mix of iGPU and dGPU depending on the workload (ex. a lot of OpenCL stuff runs on the Iris Pro). The two are in the same ballpark of performance so the setup is still a bit weird but I suppose it's only the one MBP config in any case.