Just that he has been shown, and the stuff that has been shown of him isn't really boss material by any stretch of the imagination. Also, Sakurai does not like
fake hype and has gone out of his way to explicitly deconfirm characters. For most this happened in the PotD, but for Sable it was on twitter, and for Chrom it was publicly announced or something? He was deconfirmed, and that matters. Yet this Ridley boss is stirring up all this fake hype, and Sakurai hasn't shown anything about him. Which is suspicious to say the least.