I have been in several KKW schools, some of which are, shall we say, "militant" about their teachings of the I Ching and of the relationship to the Taeguek forms. They state that the movements in the form are representative of the I Ching elements.
So let's see if I got that right: Taeguek 1 represents the "greatness of heaven", and should be performed "as such". Go ahead: tell me how to perform a low block, step, and punch "with the greatness of heaven". Or better yet, you have a new student to your taekwondo classes, and you try to convince him to perform his movements - his very first form - "with the greatness of heaven".
Some idiot came up with the idea of how to stitch concepts of the I Ching with some crap that they do in the dojang, and decided to use poomsae to do this.
I can think of no greater way to befuddle a new student being told to perform his form "with the greatness of heaven". Like, what's in store for the next form? What could be greater than heaven? (That would be a lake...)
You see the fallacy?
I think the forms were retrofitted to make them work with the I Ching. Oddly, there are only 8 forms - not 9, a revered number in Asian culture. Why are there 8 basic forms meant to tackle the meanings of the I Ching, and there are 10 yudanja forms which again separately re-capture again the I Ching elements again? [repetition intended]
I think what was meant instead is that we Taekwondo students should live the tenets espoused by the I Ching. We introduce a new I Ching philosophical concept at each level (the 8 in the Taeguek/Palgwe series, then again in the yudanja series). Ultimately, this is how we are supposed to live our lives.
What I found in the more I Ching heavy schools was a closeness toward Buddhism, and that was a turn off for students of other faiths. Also, that there is some tie-in to the I Ching philosophy and the specific techniques introduced therein, and not having anything to do with the more practical (and intended) function of a form, which is self-defense, none of this made sense to me. If I were journeying onto a path of enlightenment and following the principles espoused by the I Ching, I'm not sure I would find a Taekwondo school which would help me on that journey - even if I wanted to.
Such did not happen for me. I never sought, nor found, enlightenment. I don't even know what that means. The teachings of Buddhism, and the I Ching, and the relationship to techniques within Taekwondo all became a distraction for me. I was in it for self-defense, not enlightenment. If I wanted enlightenment, I wasn't going to find it in a strip mall dojang, it was going to be in a Tibetan mountaintop temple. (Or maybe that temple in downtown Newark...)
Bottom line, I was part of these schools which focused more on the I Ching, but I realized I lost out on what Taekwondo was really about. I dismiss the concept altogether, except as a cultural relationship to the Korean people. Is it useless? Not really, but it depends on how it is taught. Either, it is all-out and everything about the I Ching, or stay away from it. And either way, don't try to tell a white belt that his first form has to be performed with "the greatness of heaven".
And yes - seriously, that is how my schools wanted me to perform Taeguek 1 - with the "greatness of heaven". I earned my yellow belt, ostensibly after performing my form with the greatness of heaven (or living my life with the greatness of heaven).