I like the mental model and I have often witnessed the meddling you mentioned. My favorite kind of meddling: The current state of a software product is presented to C-Level. After listening (usually) for a few minutes one of the most senior people in the room starts expressing a strong opinion about how a certain color should be changed. Now the color scheme discussion starts. The complexity of enabling an interaction of a user with the software through the interface is not discussed at all. At least changing a color usually doesn't harm the usability too much.