Hello, author here.

It's actually more efficient to do a hybrid approach, especially at high view distances. Rasterizing triangles is extremely fast, and is basically a perfect primary-ray intersection. Ethan Gore recently did some experiments with raytracing and said that for large scene volumes (his engine comfortably renders the entire 32-bit range, or 4B^3) it turns out to be faster to do raster for primary rays and raytrace shadows/GI.