The Yorktown (Victory) and Concordia classes feel to me like they were rush jobs--after the war began, Confed needed a class of carrier that could be built quickly and cheaply compared to already-existing classes. Thus was born a light carrier design (Yorktown) and a fleet carrier design (Concordia). The boxy shape then is a result of this "cheaper, faster" doctrine. After all, according to Action Stations, the pre-war fleet was centered around battleships and there was thus a sudden need for many more carriers when the Kilrathi showed that small bombers could easily destroy battleships. Thus, Confed had to rush a few dozen quick-and-cheap carriers to deployment during the first few years of the war as a stopgap until more powerful carriers such as the Bengal class could be ready.