Happy it helped! I also found some info about how Nintendont lets you use controllers and virtual memory cards: it provides the game with its own implementation

Happy it helped! I also found some info about how Nintendont lets you use controllers and virtual memory cards: it provides the game with its own implementation of the GameCube system calls which then use whatever is best suited for the task, even for the controllers. The USB GameCube controller adapter is completely different from the native ports in GC and GC-compatible Wiis (it's a USB HID device, while the original one sits on an internal bus). Same for memory cards, in the original hardware those sit on the EXI bus while the Nintendont just works on files on the SD card), and the same applies to the Optical Disc Drive.