They made a detailed presentation at Hot Chips.

All the component chips are made at TSMC, in various processes.

"Developed in Japan" means the same thing like "developed in USA" means for NVIDIA or AMD or Intel. You can design chips anywhere on the planet, as long as TSMC is willing to provide you the required documentation and EDA libraries (which it does only if you already are or they believe that you will be a big customer).