Of course it involves no " formally defined 'correct structure." Its not a graded hs assignment. In fact, for tippy tops, of course one needs to be able to translate what the colleges say and show. They want this ability. It reflects thinking and thinking skills more than bemoaning the lack of some formal instruction set.
If you have researched your targets and processed, you have a better idea what they want to see, what traits or attributes. Of course consulting services say whatever they want. Their business is selling their services. Most have no direct admissions experience, nor the special insight they claim. Most have not slogged through thousands of apps/supps/essays, at the colleges.
You could write about one aspect of your personality. But it needs to be relevant to what they look for, at tippy tops. Do you understand some of the attributes they do seek?
All the CC talk about “being yourself” is useless without some understanding. And far too many applicants claim they have the ECs without knowing what matters. I know this is a challenge. But we’re talking TTs, their higher level of expectations and the immense competition from kids who do “get it.”