Yeah, I had noticed that too. I decided it's because the black is stretched out where as the red is doubled up. I had tried getting them into a similar position, but the black girl just did not want to curl up, and the red girl wouldn't straighten out.
One thing I really like about that Curtus is how the black goes almost all the way down to her belly. Most of the black bloods I've seen have that white creeping up pretty high on the sides.