I encounter an occasional person who seems to think this, and I can't speak to your specific examples as to being purebred or crossbred, but I know from several characteristics there is a difference. . . . general body form, attitude and interests, fur color and texture, the lenght of the fur and the amount of undercoat. . . ..
The most distinct thing I have to say is that the Labs are smarter and easier to train, being much more interested in you and much inclined to "read" you and try to please you. They demand more of you. Goldens are loving and less active generally, but better around small children.
Why do you have this need to discredit me? We're only talking doggies..