If I remember correctly, Miller (2-piper) refits pins with 100% contact, at perfect perpendicularity, just because he wants to. In one of those discussions, it was pointed out that neither the pin, or the hook maintains 360 degrees of bearing, and so, perfect cylindricity isn't functionally necessary. The joint between hook and pin is no longer concentric when one or other is worn. They both will need attention if you change the pin. They still won't match. The joint tends to wear in an elongated fashion, because we fire right barrel first, and the joint twists.
I have never seen a rule that said material could only be removed, never added. I believe in almost all cases, material can be added, and then the joint fitted, with less work than setting up to grind surfaces, and draw bore holes. In my view, the repair just needs to end up as invisible as I want.
With the limited use most of these guns see in their second incarnation, I don't think a head to head exhaustive test will ever occur.
They are meant to be used, and refreshing done. The American collector marketplace differs from the European in this regard.
The craftsmen that are devoted to these almost microscopic repairs are working to much finer tolerances than the originators.
