Oliver 101 wrote: This kind of knowledge is almost lost today.
Great to see that someone is still able to teach this.
A very common move in TCMA, northern and southern styles alike. Very useful in sparring.
In our Yang branch, rolling over the elbow is considered to be hidden in the form in the transition into “single whip”. The right upper arm in the vertical hold ball position is a parry parallel to the opponent’s left hand. Your arm follows the movement of his arm and folds over the elbow. Your elbow sinks over his elbow, taking his balance and the hand can be formed into a backfist if you wish.
But you are correct that not many tai chi schools teach this movement. For yang schools especially, there’s a conception of never raising the elbows to not stop the flow of qi. Ridiculous as it might seem, this idea really affects these practitioners appreciation of what is correct application of movements.