If you get a good machinist, it will be shiny anyway.
Mike.
Hi, I'm 3Vo's significant other.
I studied mechanical and industrial engineering and was trained to be a machinist.
The part when designed will have a specified 'surface finish', that is specified in 'microinches' by the designer. The smaller that number, the smoother the surface will be finished to. The machinist will produce the part to the size, shape, and within the tolerances specified by the designer (engineer) including SURFACE FINISH. The 'smoother' the finish, the more work it takes on the shop floor. So usually only as flat and "shiny" a finish as will suffice will be specified because of the additional work involved to get a flatter smoother finish. Which adds to the cost of manufacturing that part.
Bottom line, the cheaper the part is to make the better.
So a shiny smooth part was specified that way, otherwise that machinist will probably be fired for wasting the time to put that finish on.
Once in awhile for a display or promo rollout, extra work will be taken to smooth, buff, plate, and polish, but that is the exception for the showpiece.
[example, only the very first shuttle sent to orbit had painted white fuel tanks. That added a LOT to the cost PLUS the weight of the paint. All the rest have looked rusty or tan/yellow of the insulating foam....]
Even in our highly automated age, it still costs to do additional work to produce a smoother finish and the bottom line is they will only do what is necessary. Rather than machine from a solid block at a certain point, a part will be cast or pre-formed then the fine machining to tolerance is done after.
A good machinist is economical in work and TIME expended and does hold tolerance as required and specified.