What if it was really tight and we weren't sure we would make it and ran and jumped on the earlier train. Would the conductor let us change tickets on the train? Or bad idea because trains do sell out sometimes?
As mention above gates close 5 minutes before a train departs.
The conductor can change your ticket on the train.
If the train is sold out you might have a problem. Not sure what they do in this situation. I seen several wrong train situation, as long as there space the conductor just takes care of it. No extra charge, very little fuss. A few minutes maybe figure out what happened.
A lady next to me (NYC to Albany) change her ticket to a day early, but board the train going north a hour early than her ticket. She was a bit frazzled by what was going on. The conductor figure it out and then told her what happened and said “Got it”. Then moved to the next row. No fuss from the conductor. Lady was quite relieved, right into the train stop and back up to a station for police activity ahead. Her words afterwards are not fit for this forum.
My thing is after traveling for two day, maybe a few hours in Chicago would be a nice break.