Pablo, 2 thou depth doesn't sound a lot but in the context of a machined mirror finish, its obvious to the naked eye.
HC, i think you are being selective with your corrosion!
Corrosion would not have been visible in that location on REDW with the naked eye as it would have been obscured by the plug.
Not sure whether the other corrosion on the main shaft was 2 thou deep and I frankly doubt that it is visible to the naked eye if it only became apparent on the CHC shaft after microscopic inspection.