Well this statement isn't exactly groundbreaking. It's been the law in Federal Court at least since Carroll v. U. S. in 1925 and was applied to the states in Wolf v. Colorado in 1949.
I believe a case before SCOTUS, Terry v Ohio, has also ruled that an officer may not stop a person because of moving violation, non- working safety equipment or such and then demand to question or search the person or the vehicle for a totally different reason, like where are you going, where did you come from, state your business, etc.