Unfortunately the index behind the games explorer is still a case-insensitive index by FEN. That is, it doesn't know the difference between a white pawn and a black pawn.
This is explained on page 7 of the Games Explorer thread Thread 57414
. As a quick demonstration try the "cxd4" link here:
This kind of thing is surely going to make the percentage statistics unreliable as soon as any pawns reach the fifth rank. The same bug affects www.gensunasumus.com and caused me a lot of grief when I was using that site in 2005/2006.
But once that's been fixed it will be a strong contender.