If you were around dog breeding about 15-20 years ago (even as recently as 10 years ago), just about every "pointing lab" breeder seemed to keep a few intact English Setters on the grounds. If you hung around a bit more, you'd even notice puppies that looked a lot like labs but had quite a bit of white on their chests.
It is pretty widely accepted in the PNW that pointing lab stock was liberally infused with English Setter blood to help get it off the ground. It slimmed the labs down, gave pointing instinct and, most importantly, the setter's genes seemed to not do too much in terms of changing the lab's appearance other than adding a bit of wave to the coat (didn't seem to change the density, though), slimming them down some and gave a slight narrowing and elongation of the snout. Of course, first generation out-crossings often produced pups with some white fur, but it was never very much. The pups were bred back to labs to get them all black again, then their offspring re-bred to setters to get more pointing instinct. Make 'em black again .... rinse, repeat.
The lines are pretty set now from all the previous out crossings so you don't see the setters hanging around anymore. But if you were to do a deep dive DNA analysis of pointing labs, you'd find English Setter blood, for sure.
Not a big deal, really. All the breeds we love were started the same the way. The pioneers of the pointing lab world saw a market and went out and did something about it. They were right, as pointing labs are extremely popular....rightfully so for folks who hunt upland birds and also hunt waterfowl.