Sorry, but castrating a boy does not in any way, shape, nor form make him a girl. He is still genetically male, now just a male mutant. Artificial hormones may produce feminine features, but, he isnt a she.
You're so un-PC! [By the way, an over-enthusiastic castration doesn't make him a mutant, just mutilated] Next you'll be saying that poking his eye out wouldn't make him a cyclops.