While someone posted that you're paying for distance, not time, I disagree I feel you're also paying for time and if a train is early to an intermediate stop, you are entitled to occupancy until the scheduled arrival time.
I'm with you in spirit, but unfortunately there does not seem to be anything in Amtrak's publicly stated policies to support the "time" argument.
Amtrak's website describes tickets as being valid "between the stations listed on the ticket." I do not see any reference to having the right to occupy accommodations until a stated timepoint, only a stated destination. Like I said upthread, the best course of action (IMO) is to do precisely what you did...consult your SCA. But approaching it as a "right" as opposed to a "request" may not be a good course of action.
Okay....time vs. distance...consider this scenario....
The CS is seriously delayed (say4 hours or so) on its southbound trip. You are scheduled to get off at Sacramento at 6:35 AM. Another passenger, who was in coach already (due to sleepers sold out), but had paid to get your room at Sacramento on to Los Angeles, mainly to get the included meal benefit, is now delayed until around 1035 AM to move over to the room....who gets the included breakfast? You, (you normally would be off before), or them (they paid for it)?
I don't know what Amtrak policy would be in that situation, but as a way of compensation for the lateness, you probably both should get the comped meal......