I guess that was true in the earlier roomette's...the later ones had the "cutaway beds", along with the heavy zippered curtain, that would allow you to back out a bit into the aisle so you could raise your bed long enough to use the toilet during the night.In many of the old style sleepers many rooms were set up where the toilets were not accessible when the beds were down, the public room was sort of needed.
The public room for the use of adjacent diner patron's, is a good reason to explain them still being necessary. IIRC, the public toilet also was for the benefit of the Pullman era Porter, who did not get a full roomette, as Amtrak
attendant's do, but rather a sort of open lower section. When Amtrak converted these cars to HEP, they combined that porter's section with the adjacent roomette into a handicap accessible roomette...