Many years ago in fractional motor drives we formed splines with a hard PM gear with spline ID, and pressed it onto a softer shaft. This gave an intimate broached fitup, no clearance. I wonder if a secondary induction HT could have been done on the shaft after assy.
I would recommend against using a spline to locate any type of gear on a shaft. Even a root-fit type of spline. The spline should only serve to transmit torque. Add a couple of close tolerance diameters or a taper to the shaft to accurately locate the gear.
