That was in ISP document 32--but that's because it was a retelling. Doc 32 was written by ISP Detective Talbott. He was writing down what Moscow Sgt. Blaker said to him as a summary of the situation.
So, Blaker got it wrong in his summary/retelling and Talbott merely documented it.
The blood was on south side of the house, towards the west end. Maddie's bed was right up against that wall (the head of the bed directly up against the west wall, the side of the bed along the south wall of her room). And Ethan's head, as was said in the police reports, was up against that wall.
Gray Hughes does a good visual explaining it right here (and if you go back further in the video he uses some of the crime scene photos, the girls' social media, and his 3d model of the house to show how the bed, Ethan's body position, and the outside stain line up.