I guess my feeling on this is that take any of the closely related set of breeds and or breeds which had some hand in the forming of the golden retriever breed... and you will be able to spot similarities or sometimes relations probably would astound you.
Probably a good example of that was I showed a breeder friend a picture of a mismarked golden retriever and asking her how on earth something like that could happen. Literally this golden looked like a golden retriever but had this huge white stripe going down its nose.
This breeder friend enlightened me on the water spaniel background behind goldens.... including pictures of those water spaniels that were so prominent behind goldens. And you know if you look at the picture below - these dogs looked more like today's water spaniels (Irish Water Spaniel, Portuguese Water Spaniel, American Water Spaniel).
^ Tweed Water Spaniel
^ Culham Copper, who is in every golden retriever pedigree - who had a lot of white on him. And looking back at those water spaniels, not surprising to see that white, I guess.
The origins of the golden retriever breed back in the 1860's was a combination of water spaniels like above... and a yellow flat coated retriever. And there have been many combinations of other breeds (setters, other retrievers, etc) since that time to form the golden retriever breed that we have today.
I think the biggest thing you know looking at golden retrievers as opposed to flat coated retriever - especially if you own both breeds yourself or train around other flat coats... they are completely separate breeds. Whatever similarities there may be between the breeds. Similar to goldens and labs being completely different breeds - despite the more prevalent similarities between those guys!
While flat coated retrievers were in one way or another mixed in with the goldens at one point during the development of the golden retriever breed, there has been about 100 years worth of difference between the breeds since then.
I think you have a lot of us golden people bristling about some people saying that goldens are just long haired labs.
Imagine the flat coated people who have that with every mixed breed that is long haired and black and likely a lab/golden mix being identified as a flat coated retriever. I don't mean any offense to people here in saying that... I just still am scratching my head about a couple of the threads that were dumped into this new forum. o_O