Is that how the wii u ran wii games? The 3ds also showed the old ds interface to configure ds games.
I’m not sure if either one actually just dropped a second soc in there though
More or less. The Wii U is architecturally very similar to the Wii, just with a higher clockspeed, a couple of extra cores, more RAM and a better GPU; the Wii in turn is just an overclocked overspecced GameCube. It's possible, through a homebrew application, to load and run GameCube games directly on the WiiU.
If you're interested in this kind of thing, I'd highly recommend the architecture of consoles series of blog posts[1][2].
