Although I was exposed to this grooving technique 44 years ago, I only recently have been studying in depth the theories involved.
One thing should be noted. The piston has a beveled circumference that traps mixture at TDC, and radial grooves cause the squished mixture to shoot outward as well as inward. hhmmmm.
Also note that Vortec heads have that heavy square boss at the spark plug area that porters usually remove and smooth. Why did the engineers put that there? It looks to me that it creates additional turbulence in the compressed ignited burning mixture. ooooo, Like grooves do ????
Just some of my ramblings.