Tuning is both an applied science and an art. If the art does not respect the science and base itself on it, it will never succeed. Nevertheless, at the limits of the applied science, the art takes over, and goes a good deal further on. Is it good art, or bad art ? As is the case with most arts, the answers are not all black and white. 

If the science is not in place, the piano is not in tune. If the science is in place, and the art has been applied, the instrument may still not be in tune, compared with a better instrument. But compared with itself, it may be in very good tune. If the instrument is excellent, the difference between one tuning and another may be as subjective as a judgment of the instrument's tonal qualities.