Kata done with any weapon to me have the same purpose, that of you and your body getting used to those actions until the movements become smooth and easy. Again no different to any other activity where you drill a movement over and over again. There are finger drills done in learning the piano.
That's not my understanding of what kata are for -- what you describe is more what I'd call kihon training. Kata are encounters, whether or not there's actually another person there. That's what it's about
: the encounter.