Mine (part husky) also discerns what is "OK" and what isn't.
I think "OK" means: me opening the door to them, and saying Hi in a friendly voice.
What's "NOT OK" is, for instance, the HVAC guy coming back in to check the thermostat within knocking first. Or the plumber, who went back to his truck to get some tools and let himself back in. Or the tree cutting guy who had a ladder up on the side of my neighbor's house. In those cases, my dog will follow them around, watching them constantly, and letting out deep barks and growls. (I can get him to calm down, but I have gotten some nervous looks and comments from people).
So I guess I do feel somewhat safer?
At least, I won't be taken by surprise!
Rumo ~ rescue shepherd/husky mix