As German trained rider and researcher of equitation I am aware of General v. Rosenberg's mid-1800s text. It is about German adjustments to the faster, more powerful horse and as such may match Baucher's work. I have not been able to lay hands on a copy of Felix Buerkner's 1930's Ein Reiterleben. It will provide insight into classical German training progression, which I would like to compare to Beudant's early to mid-1900s ways to train a horse.
There is one most interesting difference between French and German classical traditions in equitation, which also holds true for classical Western riding. Only the German school speaks explicitly of the lateral setting of the poll in the yes joint. It initiates Laengsbiegung and Losgelassenheit, which in light of rolf movement research makes complete sense. The horse follows the orientation of the eyes and activates core muscles. Beudant's steadfast refusal of the ordinary turn around the shoulders and the shoulder-in may point to the same thing. These exercises demand locomotion into another than the eyes' direction. They encroach on the elementary motivation for movement. And yet, they prove to be a sometimes welcome instrument of power.
Nuno Oliveira in the mid to late 1900s, speaking of shoulder-in says it heals all. He thus reconnects to early 1700s de la Gueriniere, who used the shoulder-in to reestablish harmony in the horse's fascia skeleton.
All depends on how the rider asks. The horse is not numb. It discerns leadership and amity and full well recognizes constraint. There are differences in classic German, French and Western riding. But in the end it is quality that tells apart.
