Why the fictional Franco-Soviet frigate needs a much larger hull

Why is the Franco-Soviet multirole frigate proposed for 2010 in Against All Odds considered unrealistic?

Both countries favor domestic systems, while the computers, sensors, and other equipment for the proposed missions are estimated to require a hull of at least about 15,000 tons.

Against All Odds supplies the fictional example of a Soviet-French frigate intended to perform air, submarine, and surface warfare in 2010. Cooperation would be politically difficult because both countries prefer to build domestically with their own systems. The proposed capabilities are estimated to require at least about 15,000 tons. Server racks and computer rooms occupy a large part of a modern warship, and additional systems require more computing equipment. Recruiting people with the necessary computing skills creates a separate problem because those skills transfer readily to civilian employment.