I think it depends. I can tell you my dogs personalities and quirks inside and out. As far as why my dogs do certain things or act a certain way I can most of the time but a trainer can tell me how to fix it and more in depth why they do or act a certain way.
However, some people think their dogs do things and they have no clue on dog behavior and have it all wrong.
Ex: fido barks at everyone and raises hackles. Owner things dog is just being protective. Trainer and others with dog knowledge know fido is fearful.
Not everyone is keen on dog behavior.
I have learned a ton, but I'm no expert.
Just because you live with a dog doesn't mean you automatically understand dog behaviors. You have to study and learn what the behavior is and why the dog thinks the way it does to commit that behavior.
Some people who have dog knowledge can tell a dogs behavior or why they act a certain way and have never met the dog previously.
It's all about the right kind of knowledge