Who's denying any credit for brilliant planning, or operational, tactical, or strategic excellence of the Manchurian campaign. What I'm denying is its significance. The Kwantung army was stranded. Could they have massacred a shitload of Chinese people before they died of various vitamin deficiency diseases? Yes, yes they could have. Could they have gotten back to Japan to make Olympic and Coronet much bloodier than they would have been? No way on earth unless they miracled their way back to the home islands. By summer 1945, American air superiority over Japan was complete. American naval superiority over Japan was complete. The Imperial Japanese Navy had more or less ceased to exist, and Japan never had the fuel and transport capability to mass airlift a hundred thousand troops from the Kwantung Army back to the home islands, let alone the entire thing. By summer of 1945, Japan was reduced to transporting personnel by submarine because of American ownership of the skies, seas, and depths. Good on Zhukov for winning the Khalkin Gol battles, but they were a sideshow compared to Midway, the Solomons campaigns, the New Guinea campaigns, or Leyte Gulf.
Also, the only way the Sovs could possibly have gotten Hokkaido was with the invitation of the Americans, and for the exact same reason the Kwantung Army could not do a thing to defend the home islands: complete American air and sea dominance coupled with a total absence of the kind of transport capability to render such an idea feasible.