On Amtrak.com, when I click to book a ticket, it's for "1 Reserved Coach Seat". The full description from Amtrak.com is below. Nothing indicates that it could be standing room only. If Ma and Pa Kettle, who aren't sophisticated enough to understand the contract of carriage, buy a ticket based on the description below, particularly if they get a jury trial, they're likely to find a sympathetic court in a class action.
Airlines oversell flights, but (1) they always give seats to passengers (there is no standing room only) and (2) if they overbook flights, they offer vouchers or cash payments (via check). People don't always take those vouchers or payments, resulting in involuntary removals, but those are always offered. Amtrak does neither.
Reserved Coach Class Seat
While reserved coach seating is available on our long distance routes and many trains that travel short / medium distance routes, the train cars are different depending on where a train travels, so some of the amenities are different as well. Accessible seating for passengers with mobility impairments is available on all trains.
Short/medium-distance trains offer reserved coach seating featuring wide, comfortable reclining seats with ample legroom for your comfort. You'll find a fold-down tray, individual reading light and 120v electric outlets right at your seat.
Reserved coach seats on single-level Viewliner trains and bi-level Superliner trains that travel on long distance route have all these amenities, but let you stretch out even more, with extra legroom, foot rests, leg rests, and even curtains at your seat.
Famous for the bi-level sleeping cars, the Superliner trains also offer coach seats on both levels. While most passengers ride in the upper level for a panoramic view of the passing scenery, the lower level coach seats provide the convenience of well-appointed restrooms within the car.
Advance reservations (by train, not by individual seat) are required.