For many months I rode a rather ancient (later twenties) badly trained QH lesson horse whose back looked just like those first pictures (except he also had a very low set neck and the thickest throatlatch of any horse I’ve ever ridden and horrible gaits), a really UGLY horse. Of course I did not have an amazing conformational transition.
BUT he was the ONLY horse I have ever ridden who showed any real interest in dressagy type stuff. He seemed to think that it was really, really neat (just basic training, of course, as his prior training was abysmal/non-existent.)
After the first 5 minutes he also seemed to consider the double bridle as a gift from heaven.
You can never tell. He would have been the last horse I would have picked to train in basic dressage even at the very low level we worked on, but he was happy with the basic first steps. Since he came to me suspicious of people and VERY unhappy about being ridden at all (balking, backing up FAST) I was truly amazed by his response to my attempts to ride him at a higher level.
Good work Jealoushe!