Apparently, the phrase "tech savvy" has evolved. By evolved, I mean, of course, "mutated to mean something that has nothing to do with the aggregate definitions of its component words." To me, the phrase implies a working knowledge of and interest in the underlying systems that make something work. So buying a new car or listening to the radio a lot don't make you tech savvy. Working on a car or rewiring a radio do. Supposing I design a new and more sophisticated button to dispense treats to a cage full of lab rats. Are my rats more tech savvy?