With regard to the instincts of the dogs, and although I'm not a sports fan, I believe that everyone can learn, and I invite you to read the opinions on the instincts in protection work of Helmut Raiser. I don't agree with all of his criteria, but with much.
My concept of Real dog, of prey drive, of defense drive and natural instinct in a good guard dog, is the result of my experience in security work, reading, speaking and contrasts many opinions (to do it this forum is interesting) and the great help of my daughter. She is a psychologist and she has helped me understand many concepts about canine behavior, about natural instincts, about their conditioning, etc. etc.
Allow me to make sure you did not feel offended in any way; some of us in the forum question some dogs or things because we do not like the way things are going for the breed, and some dogs have been highly (or in part) overrated. That is why you see us sometimes asking for videos etc, analyzing a dog just based on the pedigree or sleeve work stopped being effective for some of us a few years ago. We are in search of dogs that can be tough with and without the handler on sight. Reality is, such dogs are very, very hard to find these dogs.
Now, having said all this, I hope it didn't feel like we questioned your expectations, dogs or experience, that is not the case. We all want to work together to TRY and improve the on-going history of the GS dog breed, which at least in our view, is undergoing major challenges and dare I say, irreversible ones.