Dear, I know they do not breed true because I have bred them myself. That is what I have been saying and why you can not necessarily base it on color when sexing.
I have actually found that not to be true (with my stock anyways) I have two very light chicks and two very dark chicks. One of the dark chicks had the dot but none of the light ones did and they are both going to be roos I think. Even when you are breeding these gems, I don't think you are...
Since this breed does not breed true I don't think you can sex off of the barred gene, at least I have not been able to. Only one of my cockerels is barred, while the other two arent.