I'm not an expert either, but I believe there has been a lot of sterility in the charcoal hens. Charcoal males do not have the sterility issue, so if you want charcoals you would cross a charcoal cock with a hen who is split to charcoal then you would get a percentage of offspring that are...
I cannot find a single photo of a Charcoal Black Shoulder Hen for comparison. The photo of these 2 looks blurred to me, so my eyes may be tired or it is blurry, but either way I cannot tell if they are Charcoal or split to charcoal.