The thing about hatchery stock is that they are not that great. I've seen BRs with grayish legs, off color plumage, etc. He could very well be a BR, however, the thing about the barring gene is that other birds besides BRs have that, the Delaware is one, and you can definitely have a bird who has NO Barred Rock in it, like my Deacon, who is most definitely barred as you saw. Unless you have a good eye for the Rock type and notice his off color and white skin, you'd not realize he wasn't a BR. Or, you'd think he was a black sex link male.
One case where a barring gene came out was a chick out of my Blue Orpington rooster, who was Sandhill Preservation stock, over my big red heritage line Rhode Island Red x exhibition Buff Orpington hen, Meg. The chick was completely barred, looked like any black sex link male! Many years back, I was informed that Sandhill added in Blue Plymouth Rocks to the Orp line for some reason, maybe to offset inbreeding, and somehow, that snuck in a barring gene as well as the yellow leg gene, though my bird had proper slate legs and you couldn't tell he had a barring gene unless you saw his almost striped dark blue-light blue-dark blue sickle feathers.
