I don't think they were arguing about search breadth. I think they were arguing that Go AI was already formidable in spite of GP's odd claim that search breadth

I don't think they were arguing about search breadth. I think they were arguing that Go AI was already formidable in spite of GP's odd claim that search breadth/depth is the reason why. Chess AI like AlphaZero aren't even close to 100% search breadth/depth but achieve startling superiority.