This was my understanding as well, but I might have read into it. The culture minds are in freaking hyperspace to get around lightspeed limitations on computations. He for sure can't beat that, but he could beat someone on another planet at their own game that he literally just learned in the year it took to get there. A game that permeates every aspect of their civilization.
I do assume his drone could beat him as well, but I'm not sure.