The checks are level at the skirt hem, and almost level at the waist. For the back to be down like that it means that that the side seams can't be perpendicular, they must be at an angle. It's harder to tell with the floral version, but the dip at the back is even more noticeable.
On all other patterns I've seen with hi-low hemlines the line drawings show the difference, so personally I think that this one is meant to be level - which means that the fitting on the models is way out - and unusually it's worse on the slim model than on the bigger girl. I suspect that there is a big problem with the drafting of the bodice.