Someone else posted it (but another link) somewhere else on here.
My opinion is that this is a poorly done study. What socialization, exercise and training are each puppy getting? These were also random breeds and sizes of dogs. So you can't compare the ease of potty training a German Shepherd to a breed that is notoriously hard to train because of their small bladders, such as an Italian Greyhound.
Zoey we got at 5 weeks old and Eevee at 6 weeks. Neither of my dogs have any of these issues. But they've also been TRAINED and SOCIALIZED. And yes, I'm a firm believer that exercise (which my dogs also get) plays a HUGE part in a dogs behavior.
Now, I'm not saying that there can't be problems from being removed early (ie. bite inhibition issues) but if you don't put time and energy into your dog, that $3000 puppy from the most reputable breeder isn't going to be better off than the $350 pet store puppy.