rewatchability should indicate a light-weight movie.
If you want that, you look at rewatchability, if you want something more complex, you use quality.
I think this is the underlying assumption.
Because the rewatchability rating doesn't just tell you how rewatchable a movie is, but also how good and "timeless" it is, i.e mainly how deeply it resonates with people.
This is not about picking a movie to watch again after you have already seen it once: this is about picking a movie you haven't seen but that is so good that other people like to watch it again and again.