Using kata as an example, the masters who created each kata did so very intentionally. Every technique is exactly the way it is for a very specific reason. As we all know, many of the most effective techniques have been hidden within the kata for various reasons. While hiding those techniques, the masters also put clues throughout the kata that will lead dedicated and hardworking students to the discovery of even more effective applications when they're ready.
Because of this, if you practice your techniques even slightly differently than the masters intended, you may miss these clues and therefore miss out on a lesson that the masters have left for you within the kata.
Details in kata may sometimes seem inconsequential, but it all leads to great discoveries.