Europe's version is way more dripped out
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A tactical warhead on major militant strongholds will not poison any territory. Look at the city of Hiroshima today for example.
In reality, the use of depleted uranium munitions by the PLA will cause many times more environmental damage within Chinese territory than any nuclear live testing, hence why it is important to avoid it to the absolute highest degrees as possible.
Having escalation dominance means that China can to some extent modulate behavior among a hypothetical attacker. The right to deploy nuclear weapons inside the country has a role, for example if terrorists state intent or attempt to carry out civilian massacres inside and/or outside Taiwan. Because the armed wing of KMT has essentially no response or counter to it.
Or for example should a wider full scale invasion be started by the US and China risk losing a lot of ground to US inside Taiwan, with no realistic short term plans to recapture it, the option of nuclear use should also be considered, to immediately capitulate them out of the war and allow PLA full focus to repel the US forces.
China is not Ukraine, we have a truly immense range of return options to choose from that they don't, we don't have to just sit and take an invasion head on.