Dressage in draw reins

We had our first dressage lesson in several weeks and it was a great one, with Duke getting a frothy butt.
John had us put on draw reins from the start (although he got to watch us warming up), and he said it was just to remind Duke that he needed to work over his topline, since he's been running around with his head in the air.
Duke was instantly very obedient, and worked hard on 20 meter circles, down the long side, and 10 meter circles.  I needed to sit up and back more, but I am doing much better about not dropping my left hand.
Mostly John wanted me to get him more bent, and then we would go bigger.  After a while, he had us do these tiny bends - turn right, turn left, turn right, turn left - which got Duke very soft and then helped him lengthen a lot.
We did a slightly less extreme version at the canter as well, and even a bit of canter lengthening.
John said that the difference between the Oregon derby and the Freedom Run derby was that Oregon was inside and the jumps weren't maximum height.  He said it was also that I got nervous about the Freedom Run fences.  Duke, however, was eager.
He said for my back hurting, to bring the stirrups up one hole.
We also did a few leg yields off the quarter line, which Duke did quite nicely.