ok you lost me thereThey are mongrels with a varied mix of genes. Same if you breed a sex-link mix (*star, *link, etc) to sex-link mix. Nothing wrong with the chicks at all but will vary from each other as the inheritance proportions will be just luck =:~)
More control over traits with one parent being a set type (breed) like in the frankenchicken Corn-X's and such
k/