While adjusting and readjusting is one way for a mechanic to satisfy a picky customer, the "fine-tuning" is not a requirement of ring and pinion manufacturers.
Think about it -- why does Richmond take the time to test a ring and pinion set for pinion depth and backlash and mark those settings on the set? If Richmond knows that a mechanic would have to adjust and readjust the set, why would they bother to test the set for proper mesh? As far as I know, the marked numbers are not a "starting point" -- those numbers are the specifications for the ring and pinion set.