Learning styles theory in communication, learning & memory, & cognitive psych roughly states that material is best learned if elaborated on from multiple perspectives, and in multiple modalities. Muscle memory theory (neural set pattern programming) suggests that, the more you do a thing, the more entrenched in your body and mind it becomes, increasing the likelihood of improved performance of the material at some future point. Literally, brain cells not associated with the data stream being programmed into the neural system reduce the number of connections to surrounding neurons, whereas neurons associated with the data stream will develop more physical connections with surrounding, similarly related cells.
From either of these perspectives, additional forms or sets could not constitute busy-work, as they would be interpreted as 1) different approaches to the same material, enhancing the number of exposures and opportunities to understand the content in depth, from multiple layers, and 2) a higher number of repetitions of similar movement patterns, increasing the state of the information being hardwired into the neurology of the brain and autonomic nervous system.