That arrangement still applies at Withdean and will apply at Falmer. The problem is that, whilst Falmer Station has the capacity to deal with about 3,500 passengers travelling to and from a match, it can't cope with more. Imagine the queues after a match.
LB, that raises a point I'd always been meaning to ask you. If a game is at Falmer, would there be scope to increase the four trains per hour you get to the station from Brighton/Lewes? Or would four prove to be sufficent? I'm not an expert on these matters but I'd assume due to the stadium being further out and the station closer, many more people would use the train for Falmer.