Are we sure that's not just a reflection of image quality, or even artificial artefact edited in afterwards, rather than lens distortion?
In terms of shadows, there are a few other bits that look slightly odd -- for example here, where two people next to each other have converging shadows, and one of the people closer to the bow seems to lack a shadow entirely
However, the shadows otherwise in the picture seem fairly consistent, and certainly the relative sizes, proportions and geometry of the rest of the ship and the J-35 and J-15 mockups (and the KJ-600 mockup) looks consistent with what we know of their relative sizes, and not dissimilar to how pictures of other carriers in the world look like taken from a similar angle.