That was interesting. FWIW in high school I worked in an auto machine shop, evenings and summers. I use to hate seeing those monster heads come in for valve jobs it took two of us to set one up on the grinding fixture.
GM got near Hemi performance in the big block by canting the valves to eliminate most of the shading. They felt that the little that they lost over the Hemi was made up in a lighter valve train and engine.