Some of this is just really widespread imprecise usage of terms: what really should be called "YCbCr" in digital contexts is frequently called "YUV." So-called "YUV" digital formats for video are really really common, and they're used for both NTSC and PAL. "YUV420," YCbCr using 4:2:0 chroma subsampling so the two color components are half the resolution in each dimension vs. the luma, in particular is super-common.
The Wii seems to actually use "YUV422" internally, so 4:2:2 chroma subsampling, where the chroma is only halved in one dimension. The conversion to analog NTSC or PAL signals happens later in the process. The repository here actually looks like it sets up the Wii's video interface to output NTSC progressive by default, but lets you configure for PAL with a config file.
The Wii seems to actually use "YUV422" internally, so 4:2:2 chroma subsampling, where the chroma is only halved in one dimension. The conversion to analog NTSC or PAL signals happens later in the process. The repository here actually looks like it sets up the Wii's video interface to output NTSC progressive by default, but lets you configure for PAL with a config file.