Anne--just most examples of it I've seen in GSDs have not been dogs who were with an owner they were strongly bonded with.
That would be a problem and I think is the main reason people might think SA dogs are also Handler Aggressive. I know if one of my dogs changed homes, and one of the many idiots who think you yank/kick the dogs around before you bond with them, got a hold of them, the dogs would have suddenly been labeled handler aggressive. WHY NOT? They don't know the person and that person starts fighting with them. Dogs don't view corrections from strangers as corrections but for some reason, many people don't get that....not until they are bitten anyway. Come to think of it, they STILL don't get it, even after a few stitches.
I had a dog here some years back that I talked about on other forums. He had been through a number of handlers before he came here. Socially aggressive and dominate but I took my time with him before I ever tried to correct him. He never bit me but the five people before me were more than a little intimidated by him and one of them was bitten. He was really a great dog but I had to first "detox" him , (from all the very bad handling before he got here), and then bond with him. That took much more time than most people would take but it certainly paid off.
Anyway, like I said, a strong bond is essential but most of the dogs I am talking about I raised. So, I never had a problem with that. Pedro, the one I just talked about, was the only dog I have owned who had that tendency but I attribute that to what happened to him before he got here. If I had raised him from a pup, it would have been completely different with him. Even as it was, he became a very loyal dog and very bonded to me. He changed dramatically over the course of a couple of years and I became his person. That dog would have really protected me, I have no doubt . The people who think you can't tell that, have never owned these kinds of dogs. It is clear beyond a doubt.
The dogs you saw were all imported . That requires some real knowledge and feel but sadly, many of these dogs do not get hooked up with the right kind of people.