The 2010 release is a remastering of the 1992 release (I'm sure because I have it). Being the 1992 release the first incarnation on CD of Klemperer's Seventh (I think), the 1997 one could be a remastering of the 1992 one or the Japanese pressing of the same.
When I contacted EMI about the release within the GROC series, they replied that it would have been possible, but they added that GROC was about to be considered complete.
L.