Unfortunately, I think you are right about the art aspect of it. I have seen art defined as anything made with the intent of being art, but I suspect that doesn't really translate into people's perception of it, which can be the artist's fault, sometimes. In this case, I think it's more of a problem in editing, since one can cut to a scene for stylistic reasons or because of necessity. In the case of bad scenes being mashed together, I think the problem is a necessity one. If the next scene doesn't introduce any new concepts or furthers those presented, it's a bad editing choice. Overusing glitch might check the stylistic need of art, but if the artist does not compose well, there is no substance.
For the purpose of practicing, simply breaking up videos can be pretty interesting, especially when it's a technique that not many people are used to seeing. Causing confusion or alarm by datamoshing things might count as art, if you are inclined to blur the lines a bit. Either way, I agree with you and you're not alone in your thoughts about datamoshing and its relationship with art as a label.
