Kata in the martial arts are a formal transmission of techniques- they are a way of performing the martial arts showing a particular way of moving or strategy for an encounter.
So why are kata shown differently at different times- aren’t they always supposed to be the same?
There are a couple of reasons “why” this might be the case- let’s explore a few…
…but first we need a kata to explore:
Your training partner grabs your gi lapel with one hand and punches at your face with the other. You sabaki out of the way of the strike and strike the punch with shuto ken kudai, followed by taking the grabbing arm into gyaku zeoi, throwing them down on the ground, finishing with zanshin.
You are at a seminar or workshop and get called up to demonstrate the kata, or perhaps you are teaching the kata to a mixed ranked class. The gyaku zeoi waza- taking the arm and barring it across the shoulder followed by a throw is VERY dangerous to the elbow.
Tori needs to have control, and uke needs to have mad good ukemi skills.
In a mixed rank class it would be dangerous to show- so perhaps it gets swapped out for something safer like seoi nage?
A second example would be you always do what your teacher in the martial arts tells you until you hear otherwise.
Imagine if you are shown this kata for the first time, and your teacher put a big emphasis on the striking of the incoming punch as you need to learn that part first- so you are show a big circling movement vs. a direct movement.
It’s now a bit different (but still the same), but it is tailored to what you need to take you to the next level.
Out of respect for your teacher and the tradition, if you are called up to demo a kata, you do it as your teacher has instructed.
There could be many reasons why a kata is done a bit different vs. the *official* version- assuming your art even has an official version in the first place vs. ura waza, or even henka.