Because softer shadows add to the realism, so they would have used them if they had invented a new efficient ray tracing method! Look at 5:12 in the video. The

Because softer shadows add to the realism, so they would have used them if they had invented a new efficient ray tracing method! Look at 5:12 in the video. The shadows are way too sharp. It's probably good old shadow mapping for the first bounce and then screen space(?) global illumination.