This is a development kit, so the transmitted signals / pinout could have nothing in common with regular usb-c and they just needed more lanes than one usb-c cable can provide, leading them to develop this monstrosity.
Similar to the PCIe extenders that use USB3 male to male or HDMI as their connector / cable.
More power, basically. Nintendo isn’t the only one that’s done this. Apple and dell both have laptops with them. https://superuser.com/questions/1615832/why-do-some-docking-stations-have-a-double-usb-c-plug has some other answers, such as video disabling certain functions.
This is a development kit, so the transmitted signals / pinout could have nothing in common with regular usb-c and they just needed more lanes than one usb-c cable can provide, leading them to develop this monstrosity.
Similar to the PCIe extenders that use USB3 male to male or HDMI as their connector / cable.
Can’t you do like 240w with USB C thunderbolt?