I believe Rivals lists them at what position they project at or what position they are being recruited primarily for in college if they play like 2 positions. If they play say RB, WR, QB, CB, or some multiple of positions, they make the Athlete category. For example, Cade Foster is a LB and a kicker for his team. He is being recruited as a kicker, so thats what they listed him as. Milliner had 57 tackles and 7 INTs as a JR, so apparently he does play the position. Just because Rivals has one film of him up doesn't mean that is the only film that exists.