How does everyone know the track at Moynihan before it’s announced?

I take Amtrak between DC and NYC pretty often and this always confuses me. I’ll be standing right in front of the departure screens, no headphones, listening for announcements, and somehow there’s already a huge line formed for the train before the track ever shows up.

It feels like everyone else got the memo except me. By the time it’s officially on the screen, half the train is already lined up.

Is there some trick people are using, or is this just regular Moynihan chaos?