I think you make a good argument. However, (and this is interesting...) the UK field labs are almost indistinguishable from the US/ and Canadian labs now-a-days. And their (British) style of hunting is not much changed from what it was back when. You should go on Youtube and look up some video's of British Retriever Trials. Really fascinating. (I get amused because they send their dogs with their off hand. Makes me laugh.) Wildly different kind of hunting. (Their dogs retrieve hare or whatever mixed bag is downed.)

So watch their dogs and you'll see the same intense, fast, lean dogs you see at our trials. (Maybe not as many needle-nosed ones, now that I think about it. But by no means do they look like the dogs in the show rings of either country.)