The Chinese already build some ships in modules IIRC. Given that dry dock facilities with the size to build a carrier are a limited resource the modular construction makes sense to increase carrier production output given these limited facilities like @Anlsvrthng said. They should also reduce the time required to build the first unit compared to the regular construction method of building the ship in situ from the keel up. The risk is that it may make integration more difficult. But I do not expect this to be an issue with modern construction methods.