If you can comprehend what I wrote above correctly you wouldn't be confused. I said, for the most part I would agree that performance dictate what they will produce...but not always. If I bred a dog specifically for my brood stock personally knowing about the dogs behind it, wouldn't you think I would have a pretty good idea what the bitch would produce?Again, this isn't a black or white topic. You just got to really use your head and make the best decision.
You did state above that there are too many variables didn't you? So it really depends on which variables you're taking into consideration when deciding to make a breeding.