Precision margins, electro-magnetic compatibility, a massive swath of survivability/redundancy/damage control requirements.
You can also say the same with certain commercial ships. LNG carriers for example. A huge part of these ships have to be made with steel that can withstand cryogenic temperatures because you're going to fill double walls and compartments with liquid nitrogen. The higher the tensile strength of the steel, the more difficult it is to cut, weld, and shape into the proper members, requiring ever larger machine presses. Survivability and redundancy are always in mind otherwise you cannot insure these ships, and to get insurance the ship and its design has to be approved by an international body. The sinking of a large containership represents liabilities in the billions and billions, especially when the cargo contained is very valuable. If your oil tanker is leaking after it gets rammed, the oil spill it generates would result in billions of dollars of liabilities in environmental damage, and the ship will likely be arrested and held in port by the country whose sea environment you damaged. The lessons of not just the Exxon Valdez, but also the Tanker Wars in the Persian Gulf is well kept in mind, that you might want your tankers to be resistant against aggressive acts by certain countries. Each country has their own safety standards when it comes to LNG, oil, container transport, etc., and you not only have to conform to one country's standards, you have to conform to all the countries standards that your ship intends to travel. A port city cannot afford let's say, an LNG, LPG or ethylene gas carrier going boom in its harbor, you cannot imagine the casualties this will cause.
So each kind of ship has their own set of standards. Also the PLA has its own exhaustive set of standards, China's large fleet of ferries and ROROs are all designed to military standards, no matter how innocently civilian looking they are, and you obviously understand the hidden and ominous intent for this. Its likely that the 075 isn't built to the standards of containerships longer than the Eiffel Tower --- which Hudong Zhonghua makes, or LNG carriers --- which Hudong Zhonghua also makes, because the meant criteria is different. It will conform to what the PLAN requires.