I don't think it's accurate though, because Benny in the basement refers to Teddy as Teddy when he writes "Teddy kill us both."

I also think there might be an alternative explanation for the faceless mannequin: Teddy and Benny might only be half-brothers. It's odd that one's name is Teddy Perkins, while the other's name is Benny Hope. While someone could write off that detail as explainable by a stage name, an alternative explanation is that there were two fathers involved in their upbringing. This might also explain why Teddy appears white/bleached, while he doesn't appear to require covering to protect himself from the sunlight (signifying that he does not also have the rare skin disease that Benny supposedly has). His father might have been white, while Benny's father might have been black.