Another condition that is always overlooked: while the Japanese MILITARY surrendered to the Allies, the Japanese GOVERNMENT did not. That is an important distinction to make.
The Instrument of Surrender contains the provision that "The authority of the Emperor and the Japanese Government to rule the state shall be subject to the Supreme Commander for the Allied Powers who will take such steps as he deems proper to effectuate these terms of surrender." (The first of these terms being the acceptance of the Potsdam Declaration and its provisions.)
I'd be interested in your opinion as to what else would have been accomplished had the instrument contained an explicit surrender by the Government. You state that it is an important distinction, and I'd like to get your thoughts on what was so important.