For others, here are the relevant excerpts from the Szilard petition, which is quite short and worth reading in full:
> We feel, however, that such attacks on Japan could not be justified, at least not unless the terms which will be imposed after the war on Japan were made public in detail and Japan were given an opportunity to surrender....If such public announcement gave assurance to the Japanese that they could look forward to a life devoted to peaceful pursuits in their homeland and if Japan still refused to surrender our nation might then, in certain circumstances, find itself forced to resort to the use of atomic bombs....we, the undersigned, respectfully petition: first, that you exercise your power as Commander-in-Chief, to rule that the United States shall not resort to the use of atomic bombs in this war unless the terms which will be imposed upon Japan have been made public in detail and Japan knowing these terms has refused to surrender; ...
This is not the case, the petition was to prevent the US from dropping a bomb unless Japan had been given the terms of surrender and refused them. This did not happen, and thus the situation can't be boiled down to "nuke or invasion" as there was a third option was not tried. I'm not making any further arguments, my positions on them are extreme and I don't want to try to convince others of them.
If fairly clearly shows that they were not listening to the requests made in the Szilard petition, which is what I am claiming. They did not publicly offer the terms of surrender or wait for a refusal.