The two things are unrelated. None of the lenses used in these tests are DX lenses. So that is not an issue. The issue is how a lens at a focal length of, lets say 14m appears, to the FX sensor(D700) versus how the DX sensor of the D300 records the same lens set at 14m (or any other setting).
When you are taking a photo with any DX camera like the D300 and you are shooting at a given focal length, you are recording the image at 1.50 times that. The FX camera/sensor will record at 100%, so a lens set at 14m will record a true 14m image; versus on a DX sensor/D300 it will appear to be 21m. This is advantageous for DX cameras if you are shooting telephoto (200m appears as 300m). It is disadvantageous if you want a wide angle shot. FX sensors give you true, or more wide images than a DX.
If you look at the two pictures on the porch, you can clearly see the difference.