to AbigailII: You are not right with this. Chess960 is not Shuffle Chess, where mirrored positions of course were functionally identic. You will have noticed, that the positions after O-O and O-O-O are not symmetric. Thus the existence of castlings indeed makes mirrored starting positions belong to different games. The conclusion is, that of course 960 different situations are defined.
(hide) If you want to play a game with an opponent of a similar level, you can define a required BKR range for a new game invitation. Then nobody with a BKR outside this range will be able to see/accept it. (Katechka) (show all tips)