Here comes my comments, but i am also interested to hear what others think about this method:
This method as I see it seems to be based on feel and questions about the feel at any bad stroke and a good stroke respectively, and questions related the possible reason for a weaker shot or a better stroke. Kind of guided, intuitive learning philosophy....
Overall an interesting approach, and a lot of feeding, repetition, time for adjustment, feedback.....although I think the coach here did not master the method.
For ex, sometimes she hit some poor slices in the middle of the net and coach not asking there at all (or commenting).... just feeding another ball. Or giving her two questions at the same time, in the middle of feeding the balls.
But I was not impressed with the coaching in another sense.
1. Hey, the girl is 12 years old, not 8 or 9. She is here not disciplined, focused, on her toes, energetic as i see it. She has a kind of lazy body language during this exercise. Kind of tired. She moves like an old granny, and she is 12! I think the coach should attend to that issue first of all.
2. Second, she is taking the balls (with her backhand slices) on the way down, and hitting the balls with too much contact under the ball, and a pronounced high to low and across follow through, so most slices are quite floating. At least it sounds and looks like that from this position. And I think the coach should directly comment and attend on that.
So why not start instructing her to take the balls a bit earlier, and tell her to have a more closed racket face at impact in order to get a bit more penetrating slice. And step in.
And the heck, most important...up on your toes...wake up, energy!