While looking for some other information (I would like to spinoff this thread to discuss “give”.) I found a paragraph in Von Ziegner’s book Elements of Dressage that may address the OP’s issue, or not, and seems to go to the idea of using draw reins with a horse that is not using its hind end. It is a bit counter to my intuition/theory/practice, so I put it out there because it goes to this most recent group of posts as well. It is taken from the chapter on Contact and the section on teaching the horse to chew the reins forward and downward.
If the horse does not follow the hands forward and downward while maintaining contact, one can be sure that there is something wrong about the relaxation of the back. In this case, the rider must show him the way to the ground, a very helpful exercise on a 20 meter circle. Riders who are not able to push a horse through may use draw reins for a limited time. A good rider does not need that tool.
