I am a farmer/educator that has layer chickens only, I LOVE and have experience in having all strains of White Leghorns . I have owned from 50 to 500 at a time. I enjoy the small egg business and look forward to always having leghorns and chickens.
In commercial breeding, they start with 8 pure lines of leghorns and then go down, so all commercial strains have 4 lines of leghorns in their pedigrees. So to answer the genetics quetions, no one can reproduce the stains of the commerical breeds, thus the birds bear the breeders names.