They haven't told how many exactly so no information can be extrapolated from the reported numbers. No telling is closer to presenting a very credible deterrence because the assumption could range wildly. Telling is giving some certainty to the actual numbers and if they are low, there's no point telling as you sort of lose the deterrence relative to presenting a larger stockpile. Therefore not telling would much more realistically suggest a low stockpile. It's the best way to maximise the deterrence of really having a low stockpile of nukes because you get a bonus deterrence on top of what you have (the unknown factor). All of this makes the assumption that deterrence functions the way Insignius described, which is more or less 100% bang on. It's far more likely China's nuclear stockpile is measly (compared to the US the primary antagonist) at best. Maybe possibly third highest count but there's a huge drop off between second and third.
Hiding huge nuclear stockpile makes zero sense politically and even less militarily. The only benefit is safety and savings. The USA probably has several hundred times more warheads so they can't exactly complain about it politically. Even if China's count is in the thousands, it's still quite a lot less than Russia and USA, therefore they can't complain, therefore no sense in hiding it. Nukes are not used in conventional warfare so even less reason to be so secretive.