Why Admiral Hipper-class displacement varied

Why did displacement vary among the five Admiral Hipper-class heavy cruisers?

German shipyards lacked consistent quality control, so nominally related ships accumulated yard-specific differences that also complicated operation and maintenance.

The problem extended beyond cruisers to submarines. A manual might describe how a class was supposed to work, yet the crew still had to learn the many differences of its own hull. A shared class designation did not guarantee interchangeability in dimensions, systems, or maintenance practice.