Not necessarily true. Although delivery systems are based on origninal Chinese design, the North Koreans have developed their own deliverly payload (satellites? yeah right.) program. The Pakistan's have Ghauri-II and Iran's have the Shahab-3 based on NK's (and China) designs, and could have added their deadly input.
The miniaturization of nuclear weapons, both in size and weight is a huge complex task. The NKs have no way of doing this on their own. The have cruddy little missiles, and if they even have nukes they are the size of an SUV. The ChiComs don't have MIRV. Nuff said?