(Speaking for myself here, not for the committee)

I think the idea is that it's fair use to cite fanworks which are publicly-posted. The way to cite a fanwriter's work is to grab an excerpt of text; the way to cite a fanartist's work is to show an image or a portion of an image.

So, for instance, I just created an entry on one of my favorite old stories of sanj's, and I quoted a chunk of that story in the entry. Because her story is publicly posted, it's fair use for me to grab a few paragraphs and include them in the page I created. With fic, it's easy to grab an excerpt, the same way I would do if I were posting a review on my journal. With fanart, the way to illustrate a point about someone's work is to show one or more of their images. If I were creating an entry on a fanartist, it would make sense to include a bit of that person's work to illustrate my point(s) about what their work is like and why it's unique or interesting or noteworthy.