You are correct that this is reversed/mirrored in the center. I have 3 panels so that both cross-eye and uncross-eye are visible at one time. There should be 4 panels total when crossed correctly, two opaque in the middle and two "see through" panels in the periphery on either side. It is tricky to see for sure.

The reasons why I mirror these have to do with symmetry of lensing, where the same image appears on opposite sides of the lens with black holes, as well as the mirroring effect with strong gravitational lensing, where galaxies can be seen as mirrored smears, sometimes multiple times.