You're willfully missing the point and your example illustrates it. The Tesla X has an extremely unique door design for the rear passengers. Certainly it has to conform to some requirements. Even if only to satisfy the definition of the word door. That it also has to adhere to regulations and consumer demands is irrelevant. Elon Musk had a relatively large degree of freedom, compared to many engineers at top-down car companies, in deciding how to meet those demands. You can assert that neither Elon Musk nor the engineers are entirely free. You could also observe that they exist on opposing ends of a continuum.