I think you are correct. I think they, or 'we' are doing it wrong. I know undoubtedly that you should have an air gap for it to work properly and I've done the opposite, more than once. Two reasons I think people, including me, have done this. First, it's cheap insurance, or insulation. Second, it's so easy to work with and it just seems logical to put something
in between, so Reflectix wins. I recently had a Sportsmobile pop top apart and even they had a layer of Reflectix between the fiberglass roof and the interior ceiling, with NO gap whatsoever.
I didn't know about the it actually conducting heat when used wrong though! Perhaps I should check this out!