This is primarily to achieve the desired color/markings for each respective sex, correct? Do you also double-mate for type or other features?
I guess, using Delawares as an example (and anyone feel free to correct me if I'm wrong) the males are supposed to have barred tail-feathers where the females are supposed to have black tail feathers laced with white. My pullet breeding cockerel would have darker tail feathers that would not make him a good candidate for being shown, or being the sire of sq cokerels, but would make him an excellent candidate for siring a pen for sq pullets.
And I think it's ridiculous! LOL