I don't think there are trundle beds on any ship, but I could be wrong.
According to the Triumph deck plans, cabins 1003 and 1004 have twin beds that can't be pushed together (they don't show a 3rd bed), and cabins 1001 and 1002 have twin beds that can be put together, a single convertible sofa, and an upper bed. (Unless you're
really young you'll want to get out the magnifying glass
!)
Maybe they're talking about bringing in a folding bed at night and removing it during the day?