As the top comment by /u/restricteddata points out, the argument about the Soviet role was made by Hasegawa (who the FP article did not cite). There's no refuting that the Soviet side of the story is important and relatively unrecognized (by the public). But it's hard to say exactly how events would have played out without the bomb. And the FP article's subheading, that US policy has been based on this "myth", is just a puzzling conclusion.
As the top comment by /u/restricteddata points out, the argument about the Soviet role was made by Hasegawa (who the FP article did not cite). There's no refuting that the Soviet side of the story is important and relatively unrecognized (by the public). But it's hard to say exactly how events would have played out without the bomb. And the FP article's subheading, that US policy has been based on this "myth", is just a puzzling conclusion.