Let's not forget that certain drives are intensively bred into certain breeds. Basic fetch comes so naturally to a well bred retriever that the same results would probably have been achieved working with the pups alone.Yes you can stake out green dogs on shoreline etc and start building desire to enter water or on land and fetch a dummy possibly by watching an older dog but anything further than that is just not gonna happen. My opinion is based on actually working dogs.
My experience with my two Rotts convinces me that it is possible. Both dogs were absurdly intelligent and it was very much in their nature to watch everything. They also had an ability to "telepathically" communicate with one another that was downright unnerving at times. If I staked out my Golden to watch another dog work, he'd make such a spectacle and distraction of himself that nobody would learn a thing.