This info is simply untrue. I would assume the Machine Shop manufacturing the parts is in the buisness of making money so having a name to secret to be mentioned would seem silly.
You are simply wrong.
There are only a few manufactures that make LPK parts for the masses. Even then they are only making trigger, hammer, sear and selector lever, the rest they buy by the pound and package up. He's not telling who it is because they don't do retail and many of them do NOT want their name out there. They are a manufacturer, period. Chances are you wouldn't know the name if he gave it to you. That is very common in manufacturing.