Thread:Ashleyien/@comment-918376-20150707020140/@comment-918376-20150731223616

I think the Setting Book did give some more info (probably just basic descriptions like the first one, though) ... we just don't get to see it because nobody'll scan it.

William's really popular with the Japanese fandom, that's why. Most other characters didn't get any info about them, not even Akatsuki. But there's a large number of prominent LH fans on twitter who are big fans of William, and they asked Elissa of the TRPG about him, which was why there was info given.