I believe the pitman arm is indexed, so moving it one tooth is not possible. Plus, doing that would limited/extend steering to one side.
It's tricky to center the steering wheel. The alignment rack is level. Most of the roads in the US are cambered to the right(in direction of travel) So, a vehicle that has a centered steering wheel on a flat level surface is always having to turn slightly left to go straight. Depending on the road camber, this can mean a large off centeredness(I made up a word) in the steering wheel. I used to do alignments, I was **** about having the wheel centered, yet people drove me nuts with complaints of being off centered. I finally found a road that was level, one that was cambered right, and one that was cambered left, and would physically show customers what happens by driving with them on those roads.

 

I align my semi. We make the distance between the drive axles on the passenger side about a 1/16" bigger to hold the truck against the crown. Picture rolling a styrofoam cup.