Thank you for a very nice and informative, thoughtful post. I agree with your premise.
We have often discussed on this site that form follows function. So the morphology of any breed will be determined by genetics and what they do for a living. So a coursing dog such as a greyhound, saluki, etc.. looks like they are built to run... because they are. A mastiff type looks like they are built to fight and do battle because they are... so if the presa canario is supposed to be the gripping dog of the canary islands.. it must be able to jump up, grab and subdue a bull.
By the way - I am not anti show - I had a wonderful show dog named Julius - he was great at the ring and was a multi national champion. When people came to the house and wanted to meet the dogs - they met Julius. You can guess why?
So anyway, the real guarding and protecting was left to the other 3 dogs. Shows do change the way a dog behaves toward strangers and anyone who says it does not is mistaken.
Thanks again for a great post.