Yes the grey 10x is a 2015 model. I have been told that the very last grey units had the focus improvements but I have never heard that the optics / coatings were tuned. However I do know that at least part of Nicholas Benoit's job at Zeiss is continuous improvement of the T* family of coatings so it would not be a big surprise if coatings are upgraded from time to time.
According to Zeiss, the black SFs have only had the mechanical fixes. The optics have not changed. As I mentioned before, the last batch of gray SFs had the armor and focus problems corrected, but the eyecups with the extra click stop had not been added.