I think I know how they came up with this wide chin on Oswald from the press conference. They adjusted the aspect ratio of the image. It's not just his chin that is wider; his whole face is wider.
They did that to try to authenticate the big wide chin in the Backyard photo.
I dare say they got a little carried away in the fakery from the press conference. They went overboard. But, film fakery is more an art than a science.
Now listen up,folks: If you claim to be an Oswald defender you must reject the authenticity of the Backyard photos. That's because he's brandishing the murder weapon in those photos, a weapon he denied ordering, owning, or ever seeing.
So, you want to call yourself an Oswald defender? Then admit the Backyard photos are fakes. Otherwise, you're the fake.