The above is a VERY gross generalization but I am in agreement with the breeders who look at the total picture of the dog and ensure that it can indeed do the job it was bred to do with the body it was given. I'll use me as an example- I have a very athletic build, my bones are strong and healthy, my joints are wonderful looking at the bone/cartilage aspect, I have decent endurance, and have been told I'm way too strong for my size. Conformationally, I am a pretty good example. Yet I have a condition that is not immediately apparent that makes me quite useless more often than not. So if you judge me in the showing, you'd say I'm a good specimen but if you judge me on physical working, well let's say I won't be swimming in the gene pool. :rofl1:
Which is why it SHOULD be commonplace to test for both! Work your dog all day long, day in and day out in whatever sport/venue etc is appropriate. That's great. If no one can recognize him physically as the breed he is, I'd say he doesn't need to be bred. I'm speaking in terms on purebreds here. I know there is a lot of variation in lots of breeds, border collies for one. They can come in any coat length or color, but there are other physical traits that make him a border collie. If he is a great herding dog, but someone at a trial has to ask you what breed he is then maybe he shouldn't be bred. This is what I use conformation for. To show people that my dogs are functional and they can be recognized as ACD's.
I also firmly believe in keeping the working dog in the show ring. People say, "Judges won't put up a working dog." Well, show them a working dog. If they don't have that dog in their ring, hell no they can't put it up. Not saying they always will, but your perfectly groomed barbie dogs don't always win either. There can only be 1 WD and 1 WB on any given day.