This is the type of thing that needs to be highly questioned, and not immediately believed.
Re shadowing, and she appears lighter: Does the guy know where the light sources are placed? Is there a second light source to the right near Emily? Does the guy know? No. It's all about lighting, but he has no actual idea how the lighting was arranged in the studio.
Re Emily's head is smaller: Yes, her sisters are also fatter in the face, and her skull is vertically the same size. Emily is not as fat as her sisters is what I'm thinking. Her arms also indicate she has a lower body fat percentage.
The "smoking gun" is a piece of straw in a grainy close up that "appears" to be cut off. How long is the piece of straw? Buddy is supposed to have a mess of long straw all over his knee for the photo? Sorry, that's not a smoking gun imo.
I think this guy has his mind already made up, and is hunting for any scrap of "evidence" to support it.