I do think this glass layer is significantly different from the other Nikon DSLRs. And also different from the D800. I could clearly see only 1 layer of glass for each filter. When I tear down my D7000 for conversion, it has a 3 layer in one stack and a separate dust shaker filter just like the one in D600 here. This D600 seems to lack a waveplate and an anti-aliasing filter in one direction. If you could check the dpreview resolution test, it's clear it lacks the horizontal one.
Could you measure the thickness of both of these glass using a micrometer or vernier scale?