I don't know. However, the Palace fans who had been rounded up from the bars down by the seafront and walked to Brighton Station would have been on their way, or close. I would expect that police at the stadium had to be prepared for their arrival and the task of trying to keep the "welcoming committee" away from them as best they could.
On a broader point, I really don't like the general tone of your post, and similar, that just seem to want to try and find fault with the police. Maybe they were at fault - I simply have no idea, so I'm not going to go jumping in trying to point the finger of blame. There will be debriefs and investigations to try and ensure that anything that went wrong doesn't happen again.
I don't go to football wearing a tightly drawn hood and a scarf or balaclava over my face. I don't take weapons. I don't take pyrotechnics. I don't try to get in a ground without a ticket, causing physical harm to those who try to get in my way. Unfortunately some people do, and some people have to try and minimise the impact of them on everyone else.
I have massive amount of respect for those who are tasked with trying to make sure tens of thousands of people can get to the game, and home again, in safety. I'm willing to accept that they may make mistakes because it's a really difficult job on nights like Tuesday. And I wouldn't want to do that job myself - it looks very tough.
But the point of the heaviest police presence I can recall at the Amex was to prevent disorder and in this they failed miserably. I am well aware that all the trouble was started by the scum and that they are ultimately responsible. But we have police at matches to prevent disorder so that those of us who turn up to watch a game of football can do so peaceably and without the dangers that so many faced on Tuesday night.
I am far from being the only poster to be hugely critical of the police and the way they handled the events on Tuesday night but you have singled me out for branding! Thanks for quoting my post though.