there is a legal difference between using osmc:symbol:complex_copyrighted_shape_code and uploading copyrighted image somewhere.

In similar way as I can post title of a book without violating copyright, and posting full text of book would be problematic[1]

though “Renderers read the descriptive text and render something that looks like the image of a logo” may be problematic and works only because Wandelnet does not actually really want to enforce their full rights, basically it provides plausible deniability. I would not try it for example with Disney.

[1] except cases of openly licensed books, ones where copyright expired etc