TWDuke, I think you may have hit the nail on the head in terms of practical effect, at least regarding aggression.
I used to have a terrier/poodle cross. She was about 10 lbs. She hated every single living thing that was not a member of our family, and she was determined to kill them.
NB: human babies were excepted from this, for reasons I never understood.
When I took her out for a walk she’d be all happy, tail up, ears forward, the canine equivalent of a big smile, until another person was within lunging distance, at which point she’d try to kill them.
She got into our neighbour’s yard and tried to kill his dogs. Two Shepherd/Wolf crosses. I was not happy to find myself standing there (I’d gone over the fence and grabbed her and thrown her back into our yard) looking at those two.
She was, for all of her 14 years, a completely bloodthirsty would-be killer. She also weighed about 10 lbs.
The sweetest tempered Pit, or Rottie, or Doberman, or God forbid Neapolitan Mastiff just has to have one bad day and go after somebody and all of a sudden there’s cops and ambulances and major trauma surgery and big headlines.
It may not be that some dogs are more likely to bite than others, it could just be that some of them are better at it and it tends to get the attention.
