I noticed on mine, and other's cars, sometimes the edges of the center brake light are not flush with the tail lights.

Well they'll never be, which is no big deal. But if you take off the center cover inside the hatch, there are about eight 8mm nuts which mount the actual light to the fixture for it. Loosen the nuts and push down on edges, then retighten. The gap should be less and almost unnoticable afterwards.