Let's go back to my first illustration:Now, what kind of positive reinforcement would you use instead of the one I used which is to get out of the horse's way and let him lope on for a ways. Would you stop him to give him a treat? Would you reach down and pet on him? Just tell me how to 'reward' him other than stay out of his ribs and face? Please tell me what else a trainer can do when a horse gives the asked for response under saddle? Anything else I can think of to do would just confuse the horse and erase the 'relief' he got from my leaving him alone and getting out of his face and ribs while I let him lope with no pressure on him.
There is nothing wrong with the reinforcement you used. The old pressure release as the reward is extremely effective positive reinforcement.
Sometimes it seems like those raving about positive reinforcement did not really understand what they read.