> "...If the Japanese had simply been given the option to retain their figurehead Emperor, they'd have certainly surrendered..."
There was a barely averted coup (https://en.wikipedia.org/wiki/Ky%C5%ABj%C5%8D_incident) to overturn Hirohito's decision surrender so that is clearly incorrect. The military, who was in control of the Japanese government, wanted to continue the war even after the use of both atomic weapons.