Bruce, et al;
Since the odds are that the person cataloging the photographs was not an expert on PRR cars and probably overworked and bleery eyed, how about this:
Somewhere in the stack of material was a picture of one of the X32 box cars that were converted at the direction of the AAR as prototype for troop sleepers, and hospital kitchen and command cars in 1943. The image of a box car and the caption for the hospital kitchen cars stuck in their mind and it was incorrectly labeled.
A stretch I admit, but it wouldn't be the first time captions get attached to the wrong photo, and based on my time working for a library system, not the first time the catalogers got the data on the wrong entry