MM, the k31 has a case hardened receiver with an excellent bluing. gyvle said his experience is with commercial rifles. We've never experienced nor hear of a SP aluminum mount marring the finish on a k31 rifle.
If your group is .625" to the right of dead center, the it stands to reason that the offset POI will be the same at 25 yards or 1,000 yards. If you zero your scope (with the offset) at 200 yards, you'll never note a difference at 500 yards. All of us here at SP do not zero the scope on the bullseye. If you're punching paper at a specific range, that's one thing. If you're taking game, how would .625" offset ever make any sort of a difference? It depends on the application.