The Apple II power supply was the first switching PS I had ever seen. And I still saw a lot of linear ones post-Apple II… From the article, perhaps the IBM switching PS, four years after the Apple II, then more or less cemented the switching PS for consumer electronics.
No. There was no "unit". This was before the days of modular PC PSUs and switching wall warts (which started proliferating only later). So it was just a custom circuit that used commodity components. For these components, the volume of orders from Apple would have been tiny compared to overall market demand.
What an excellent example of Brandolini's law: “ The amount of energy needed to refute bullshit is an order of magnitude bigger than that needed to produce it.”