User blog comment:B214/Volume 22 spoilers/@comment-83.52.229.235-20161115095808/@comment-10330822-20161115161823

Except we don't even know Tiamat's abilities, so you can't say she can't disguise herself as a demon. Likewise, only the announcers are referring to her as a demon, and they don't even know how she is, so they aren't exactly a credible source.