You are correct; meals are not included with coach seats on any other train. They also aren't included with coach seats on the Auto Train. I think that the issue here is that you’re thinking of accommodation in terms of a room. That’s not the correct definition here; again Amtrak is providing you with special accommodations when you pay extra for something. That something could be a sleeper & meals, or it could be a first class seat on Acela, or it could be the transport of your car & meals on the Auto Train.I guess I don't see it the same way. On the Autotrain, you don't get the same things in coach as on all other LD trains. Specifically, you get more; your meals. Meals are not included with coach on any other Amtrak LD trains, I am pretty sure.You get the same things in coach on all LD trains. So no need to call it anything else IMHO.
If I book my mom and I into a sleeper on the Silver Star, only my ticket shows an accommodation charge. But she still gets free meals in the dining car. It's included in the accommodation charge that I paid for the sleeper & meals. If I book my brother's family into the family room on the Capitol Limited, his ticket will show the accommodation charge for the room. But his wife and two boys will still get meals, even though their tickets only show a railfare.That's the same way it is on non-AT LD trains. Every sleeper passenger pays railfare, and one pays the additional (roomette/bedroom) accommodation charge. That's how it is listed on that ticket. However, all sleeper passengers get their meals, even those only paying railfare.Since it's quite clear on one's ticket, or eTicket now, that one is paying X for a seat and Y for the car, I see no need to call coach seating anything other than coach seating. The charge for your car appears in the accommodation charge box, just like if you brought a sleeper on a regular train. The coach charge is still called railfare like it always is. This coach seat is identical to every other LD coach seat in Amtrak's system. The meals are part of the accommodation charge, not part of the railfare.
As you state, on the AT, every coach passenger pays railfare, and one pays the additional (car) accommodation charge. However, all AT coach passengers get their meals, even those only paying railfare.
To me, that makes AT coach is more synonymous with non-AT sleeper class, than non-AT coach. And therefore deserved a more fitting name.
No different than the Auto Train in coach, where one person pays an accommodation charge that includes money for transporting the car and money for the meals served in the dining car for all members of the party.
One person pays the accommodation charge, but all members of the party get the benefits that the accommodation charge provides.