Besides the creepy desciption of the maturing process of 18-22 year olds (and some suggestion of racial differences)... I've never thought of kickers as having required anything other than "being able to kick". Kickers come in a variety of shapes and sizes (often times... no resemblance to the rest of the "football team"). If someone impresses the coach that he kicks the ball well... I don't care if he's still tethered to his mom by his umbilical cord.