America does not want nuclear war. China doesn’t want nuclear war either, but sometimes accidents can happen because one side could misread the intentions of the other side.
At the height of the Cold War, there was so much fear of an accidental nuclear war that the US and Soviet Union installed a direct hotline to prevent the either side from striking due to miscommunication.
2019-2020 was an incredibly chaotic period of time, especially pertaining to US-China relations. The general was just calling his counterpart to prevent any accidents from occurring.