In technical terms...yes.
But, remember, hatcheries are selecting birds for production. They will select birds that resemble the Standard, but their main focus is for birds that produce alot of eggs, so they can hatch alot of chicks...to send to alot of customers.
The "strain" is pure, however, Barred Rocks could have been used in the line WAY down the road.
True Marans, that are quality, are hard to come by and are expensive. Hatchery birds resemble these, but can have all sorts of different characteristics that are not desirable when showing or breeding for the Standard of Perfection.
Hatchery birds may or may not have the desired egg color.