CAD plating is still available at houses around the country. Generally what you refer to as shiny and dull is refereed to as type I and type II CAD plating. In order to achieve the bright finish plating shops will add brighteners. This is just a visual preference by the OEMs unless they are plating higher KSI steel, usually above 160-170. Materials with high strength are susceptible to hydrogen embrittlement and brighteners add to that effect, This is why you hear people talk about post plating bake (embrittlement releif)

The brightness of a detail is not a result of date, but a result of base material finish and engineering drawing requirement.