It implies "starting" a nuclear exchange. But the Chinese targeting model indicates that they have (according to THEIR estimates) no hope of WINNING (big difference) a nuclear exchange. Basically, Chinese nuclear forces are the last line of defense for Chinese sovereignty--they are intended to prevent the US (or anyone else) from engaging in actions that would lead to the destruction of the PRC as a political entity, by threatening unacceptable levels of damage in return for those actions.
If they seriously intended to fight and win a nuclear exchange against the United States, their force structure would look a lot more like the XUSSR's did at their peak.