I doubt that. A conspiracy too far. They bought a half-year supply in six weeks before the attack. I don't think they would have done that knowing they could get it $250 per oz less a day or two later.
I think China and Russia were very happy with JPM and GS keeping the POG at around 1550-1600. That gave them stability for their buying programme.But their assets have been damaged by the POG at 1370.