The Korean War did not happen until 1950 so the press release during WWII cannot tell us anything about Truman's thinking in Korea.
In Korea, his decision not to use the bomb had to do with the changed world circumstances. For one thing, the Soviet Union now had atomic bombs. In addition, the Cold War was in full swing and Truman worried that using atomic bombs would cause the Soviets to retaliate in some way. He worried, for example, that they might invade Western Europe. This worry was reinforced by leaders from Western Europe who did not want to face the possibility of Soviet action.