But are they confined to Bohai Sea or SCS?The Trident II may be multiple decades old, but it is still in service. A variant of it is supposed to stay in service until 2042. The current Chinese JL-2 range and accuracy-wise has probably around the same capability as the Trident I.
In any case, the Trident II's fearsomeness is not because it can hit Asia from the Gulf of Mexico, it's because US subs are deployed all over the world. In that case the range is not so important. If China's subs are confined to the Bohai Sea or the SCS that's their main disadvantage.
Do you have any reports about deployments, numbers etc?