We have seen a number of puppies, especially the ones that tended to be quieter and less dominant, simply blossom. We had one puppy that, when we sold him, was a very soft, very mellow, easy-going puppy that would wilt if given a strong correction. When the owner called us nine months later with a behavior problem, what we found was a very strong-willed, confidant adult. The owner was still correcting him like he was a soft, mellow mush. Once the owner became aware that she now had to correct him stronger and that he would no longer wilt, everything worked itself out.
Every breeder works their selection process differently.
Some breeders pick the puppies for the new owner, some give the owner full reign. We take a course somewhere in the middle. We may make recommendations against a particular puppy that we don't feel would be a good fit in their home and what they might be facing if they did choose a particular puppy. We do, however, let the new owner have the final decision. Each and every puppy in their litters will receive all of the necessary care and attention that they need in order to grow up into happy, secure adults.