Not a bug but the "Tags and Sex Contents Definitions" does not contain a description for "Illustrated", not even "self explanatory".
However that isn't the point of this post.
How few illustrations should there be for a story to qualify as illustrated? It could argued that a single illustration follows by text isn't an illustrated story, it is a story with cover art.
The old pocketbook/novels almost always had an illustrated cover. None purported to be illustrated. Laving aside the discussion of whether a picture and a couple of paragraphs of text actually qualifies as a story, shouldn't "illustrated" require more that just a single illustration?
A common writing challenge is to choose (or be assigned|) an illustration to inspire the writer. A past SoL competition was based upon a picture challenge. (The Knocker) None of products of these challenges are considered "illustrated", even though the illustration is usually included ahead of the text.