Well I'll take a shot at this being I think I understand your question.
First off the NEC doesn't have anything to do with city of CHI itself. The NEC is simply the route located in the Northeast US in which Amtrak owns and dispatches the majority of (with a few exceptions). However, to answer your question, it is a fact many times trains are held for a few minutes to accomodate late arriving "connecting" passengers. I have seen it in many occasions in many places. It doesn't happen very much in places like NYP due to nature of rail traffic flow, but one time on train #97 we were held at NYP to allow some connecting passengers to arrive and board the train. We were able to make the most of the time by the time we made WAS. I have experienced many times being held in WAS to wait for the train #30 to get there to make connections with #91 when it was on the old schedule. I have seen the former "Sunset Limited" held in ORL for our arrival on train #98 for multitudes of passengers. I have been held in JAX on the old "Palmetto" to wait for a insane late "Sunset" to allow passengers to connect to it who were supposed to catch #92 earlier that evening, etc.
I see the point you are making, and actually in Amtrak's defense, it makes better sense to accomodate late passengers (when it is Amtrak's or other operational reason/fault) the best we can on another train if it is available. Amtrak's goal is to get you there, maybe not exactly when they say they will, but none-the-less..... getcha there! LOL... Anyway, that is certainly one of the many reasons on time or slightly late trains become later trains. I will say this, however, just about all of the passengers off a late arriving connection are usually VERY HAPPY we waited for them. Unless it is only one or two people making connections, it is actually the right thing to do!
A few years back we had to wait outside RGH for the arrival of a rather late "Piedmont" (which is never really late at all) because there were several passengers making connections to #91 there. We were on time, but in the end by the time we left RGH we were over an hour late. But CSX didn't let us down, and we were back on time by the time we left ORL the next day, and made it to MIA on time (that doesn't happen much anymore)! OBS...