In Wolf Lowenthal's book There Are No Secrets, the author presented a situation in which Cheng Man Ching had asked the students to push hands without using the arms.
The students were using tension.
They were forcing a result.
Cheng Man Ching wanted the students to push hands in a different way.
However, he was not prepared to explicitly tell the students what to do.

Years of fruitless practice bore no result.
After Cheng Man Ching's death, the author was watching a video of the instructor pushing hands when he suddenly saw how to push hands correctly.
In hindsight it seemed obvious.

Cheng Man Ching was not keeping secrets. In fact, he was showing the very skill all the time. But his students were just not ready to see it.

Think of the treasures as being like this example.

The 6 balanced pairs can be considered in more detail:

1. Hands & feet
   - hands and feet must coordinate
   - if the right hand is yang, the left foot is yang
   - the further past the feet you extend your hands, the less centred you are
    
2. Elbows & knees
   - elbows and knees must both be naturally relaxed and in-line
   - elbows and knees do not initiate any movement
   - knees are soft and loose, not locked or collapsed
   - elbows are dropped and heavy
    
3. Hips & shoulders
   - shoulders must be above the hips
   - do not lean upper torso forwards or backwards
   - vertical distance between shoulder and hip should not increase or decrease on either side
    
4. Back of head & coccyx
   - the base of the spine and the base of the skull move together
   - this encourages moving from the back, and remaining upright
    
5. CV1 & crown
   - CV1 is between genitals and anus
   - the centre of the skull and CV1 must be joined by a vertical line
   - this is your vertical centre
    
6. Buttocks & armpits
   - armpits are open, buttocks are drawn inward
   - do not tuck the pelvis

Throughout the tai chi syllabus there is a need to grapple and to avoid grapples.
Yet, grappling is tiring and wastes time.
It is necessary to avoid being held.

Shuai jiao offers leverage principles that enable the student to evade holds with ease.

From the very beginning of their training students explore:

1. Against a grappler
2. Escapes
3. Floor work
4. Floor work (control)
5. Freeform grappling
6. Monkey paws
7. Pushing legs
8. Yielding/chin na

Escapes and floor work are particularly important skills.
They enable the defender to remove themselves from harm without the use of brute force.