I've read that argument, and I actually agree with it. Would Japan have surrendered after seeing an uninhabited island nuked? Almost certainly not, but it would have given the USA the moral high ground, and perhaps set an example of how nations should behave.
I also understand the arguments against it. There were only a limited number of A-bombs. And a dud A-bomb would have done nothing but strengthen Japanese resolve. And lastly, 1945 was not an ideal time to be concerned about any moral high ground.
We only had the two A-bombs; Fat Man and Little Boy. Both were totally different designs. They weren’t sure if one, both or neither of them would work.