I worked for a Chrysler plant that made torque converters. The hub (the part that goes into the transmission) was ground to size, and then "polished" to make the ideal surface for seal wear. The funny thing is that the "polishing" actually produced a rougher finish than the grinding.

Haha! Maybe they wanted some scratches in there to hold oil like piston ring cross hatch marks? Seals like a little lube,