My barred rocks didn't look much like that when they were that age. I ordered mine because the original batch of chicks I got at the local feed store had them all labeled wrong. Like what was supposed to be a leghorn turned out to be a white EE and my black australorp ended up being a black copper maran. I REALLY wanted barred rocks so I went to the extra expense of ordering them. (They are so pretty.)
I think the feed store just gets a mixed bag from the hatchery and then take a good guess as to what breed they are.
I make a point to get mine direct from a hatchery from here on out.