The raytracing is, but you don't see the result of the raytracing, you see the output of a neural network inventing detail based on higher definition training data. It's like seeing some blurry dots through a microscope, then drawing a sketch of detailed cells, based on your memory of pictures you've seen. The microscope is an optical system, but the sketch is the result of memory and style transfer, not simulation of optics. Hypothetically, you could have no understanding of the behaviour of light in producing the detailed sketch.