Yes, his GPU has not been maxing out except for 4K (which is irrelevant here). You can say that it was in Witcher 3, but Witcher 3 is quite a balanced game and will eat up all the hardware you will feed it. However it scales so much better with a processor as you can lower heavy postprocessing options to significantly decrease GPU load (especially on higher resolutions) but with the processor load there is not much you can do.