Policy is political and will change if the situation changes. If China was the only one in the world with nukes, of course they'd use them.
China's warheads are also generally higher yield - they're intended for counter-city ops, not counter-force.
The idea with the currently deployed warheads is that even after losses to a hostile first strike, they can still respond and cause unacceptable losses in the enemy. How many nukes does it take to cause 10% fatalities in the USSR? How many in China? And what percentage of those nukes are destroyed before launch, and how many make it though enemy defences to detonate where they should?
China's warheads are also generally higher yield - they're intended for counter-city ops, not counter-force.
The idea with the currently deployed warheads is that even after losses to a hostile first strike, they can still respond and cause unacceptable losses in the enemy. How many nukes does it take to cause 10% fatalities in the USSR? How many in China? And what percentage of those nukes are destroyed before launch, and how many make it though enemy defences to detonate where they should?
And of course, nukes decay.