I feel like if you have a controller that is branded for both, the latest released console should take priority if you had to pick one. I can't imagine they would market a controller towards the 2600 and say "but wait! You can also play this on your Genesis"
![Tongue :P](https://vgcollect.com/forum/Smileys/default/tongue.gif)
Even if they did, it just makes more sense to pick the later console.
Besides, the Fighting Commander Controller is only marketed to the SNES classic, not the Wii U or Wii at all. The NES classic extension cables have a very small blurb that they can be used with Wii or Wii U Pro Controllers, but that's it. It says "For NES Classic" right on the front of the box.
IMO it
only makes sense to make a dedicated console "accessory" section under the dedicated console subheading for this, the NES classic controllers and extension cables, etc.