Hatcheries sometimes propagate a bad strain in a certain breed. Could happen with Rocks. I hated Delawares after having some evil vampire chicks I hatched from hatchery stock parentage. HATED them. Delawares have an awesome rep as a calm, uber-friendly bird, but not those! A breeder talked me into hatching some from her quality flock, said they'd be different and they really were.
So, although Barred Rocks are generally the absolute best friendly, curious, calm birds, there can be exceptions. And trust me, they are exceptions, not the rule or I wouldn't be of the opinion that they are the best, all-round breed on the planet.