It's the same thing with GC/Wii and TEV, TEV is very similar to the N64 combiner in many ways: You basically configure the pipeline in a relatively fixed way, but it allows for many different ways to combine textures into one (hence "combiner") that is actually far more flexible than the early programmable pipeline, which is why the GC/Wii and N64 are able to do things that are otherwise difficult using traditional pre-SM 1.0 rendering techniques.
While the N64 and GC/Wii don't have actual shaders, it's ability to be "reprogrammed" in such a way is very analogous to Shaders, so the confusion is understandable.