I rode #1 all the way in 2017. Most of the people we sat with in the diner were USA or Canadian citizens; a minority were part of European tour groups.
Very few diners, no matter where they were from, left tips for wait staff. When I tipped, there was at best some unflattering looks, and also a couple of verbal disagreements. It seemed like they didn't want me to tip because it made them look cheap.
Part of the change in tipping, I think, has to do with the fact that meals are included for sleeping car pax. If you don't get a check 20% of zero is zero.