Being just a prototype it might just have been enough to test, like the test Starships these days. Once you can cruise you can trade passengers/cargo capacity for fuel. But probably all the numbers were quite aspirational.

Also it probably would have followed a flight path similar to the Curtiss NC-4, with refueling stops, leaving the longest leg to be between the Azores and Newfoundland. Still much farther than the range though.

I think even if they could make it work though it would have been awful for a passenger. The cruise speed listed is incredibly slow. NY to London would take almost 2 days of flight time.

Compared to two weeks(!!!) by sea, which was the norm back then, two days sounds really impressive.