Sexing/cloning

During my research i found a video that started the flowering stage very early (~4weeks) to determine sex. then once they got a healthy female, they cloned that plant and resumed 18/6. How well does this work as opposed to just separating out the males? anyone had good experience with this?

heres the link from one of the threads Stoned Free Guide to Growing Cannabis. - Google Video

They take out the males as well.