I do believe that is exactly the case. It would be no different now if you went to your local FLAPS to purchase a headlight switch and they handed you a Bosch equivalent or similar. I have never seen them in the kits and if you went to a GM dealer parts counter and asked for a replacement switch it just makes sense you would get a part from the General Motors Parts Division in most cases.
Look at this switch box detail, that is a lot of models spread over 20 years covered by one switch. How difficult is it for the local dealer to say keep four on hand that covers 20-years of vehicles.
https://www.flickr.com/photos/advance-design_parts_co/15256453904/in/set-72157631868452754As far as the Ark-Les switch goes they look similar enough that most people would never know the difference, but that wasn't the question.
