Yes, tour groups CAN have first "priority" for lunch and dinner reservations on the trains. I have experienced this "travesty" myself , on the Zephyr.
I will share one memorable experience. I was westbound on the Zephyr. A large tour group (in coach) boarded at Reno. I thought nothing of it. I was seated in the Sightseer-Lounge car as lunch time approached, prepared to soon enter for lunch.
Well, without notice, this tour group marched through the car to the diner "en masse." I remember some of the members of the group even saying , "I guess we're first to lunch !" I was stunned to say the least. This was at about 11:30 am. It was not until 1:15 pm that the group exited the dining-car ! I , of coursed , "fumed" (along with every other first-class passenger forced to wait.)
IMO, this is yet another example of where the lack of leadership at the top really hurts Amtrak, and makes intercity passenger rail advocates look like fools.
To me, incidents like this happen because some middle manager somewhere has been browbeaten. Someone with control over that individual's job has said, "Take care of those tour group passengers." By the time the message reaches the train crew, the message has become, "Pamper the tour group passengers -- do whatever they want -- or it's your job." If Amtrak had adequate leadership, the tour group would be advised some members might sit at 11:30a for lunch, some at 12:30p, and some at 1:30p. I'm sure SDS only amplifies the whole "tour group at lunch" problem.
Which of course brings up one of my biggest pet peeves about Amtrak dining. Why in the world in this day and age of computers that can suck in and edit HD video can Amtrak fail to see if patrons want to have a meal in the dining car when they purchase a ticket? Why? If you're in Amtrak management lurking here, please offer an explanation! I have on the shelf near this computer an Atlantic Coast Line timetable from 1967. In it is an advertisement for meal tickets one could purchase in advance. If ACL could offer such services in 1967 without benefit of computers like we have today, why the crap can't Amtrak offer gift cards that one could use in the diner -- AT A MINIMUM? Ideally, at the time one makes a coach reservation on Amtrak, one would be given the opportunity to purchase a meal in the diner. Such an approach would help manage the flow of people into the diner. For all we know, it might mean SDS is inadequate for LD trains at certain times of the year, and a different approach (such as running the diners in "the grand manner") might be required. It's called "upselling", people. It's done in every other industry except Amtrak, it seems. As I said, if anyone from Amtrak management is scanning this forum, please attempt to explain to us why. This is a leadership issue, so saying "it's the money" doesn't cut it.
Perhaps it's time for a letter to 60 Mass on this subject.