I don't think China's nukes would be much of a deterrent to the most likely scenario, which is US military support for Taiwan in case of an invasion. They aren't going to able to credibly threaten a first strike nuke attack to deter the US, given the US can and will retaliate vs any nuke attack with a nuke capacity at around 20x that of China's.

I think Hu's talk reflects fear that the US would be tempted to use its nukes in a first strike capacity, given that China only has two legs of the nuke triad (ICBM and subs). Given the geography, it may be possible to bottle up Chinese submarines in shallow waters, and given the increasing sophistication of anti-ballistic missile defenses (especially new research into directed energy), there is the concern that deterrance has less of an effect on the US.