The race engines we used to build got a hardening process on the crankshaft journals which required the shaft to be straightened and re-polished after the procedure, but I can't remember the name of it. I believe it was called "Tufftriding". Unless the hardening on a crankshaft goes extremely deep, I can't believe the hundreds of thousands or maybe millions cranks that have gotten reground 10, 20 or 30 thousandths undersize in the 50-something years I've been fixing cars are all running without being re-hardened. I can see an advantage to doing some sort of hardening process on cam lobes, but since we're discussing resizing a round area without lifter pressure, it doesn't seem to be that important to worry about the hardness of cam bearing areas.
Jerry
