I would say that there is more manipulation in straightening than just scrunching, plus I believe there is no way to make your hair "curlier" with products. I think it just enhances what your hair can naturally do. My hair curl pattern does't change without products, but it sure is frizzer.
For example, if your hair isn't moisturized and is dry, and your curls appear limp. Does adding a moisturizer or product to your hair change the way your curls may appear? Yes (giving it spring and bounce) , but does that mean the hair cannot naturally do that on it's own if it were moisturized? I don't think so.