Students are taught according to their ability to understand.

If the advanced level of practice were offered to a student of a lesser grade, it would be entirely meaningless and confusing.
The student lacks the cognitive skills and the physical awareness and sensitivity to understand what they are being shown.

Therefore, students are shown what is necessary. They are offered a pared-down, crude outline of the real thing.
As the student proceeds through the grades, they unlearn, dismantle, reconsider...
The material slowly becomes more accurate and internal.

The danger lies in quitting at any point during this learning process, for the student leaves with what they have learned to date and mistakenly believes this to be the end product,