It is just that it is surprising after a quick ramp-up over the past decade to see the dry docks empty like this.
Is this a shift in priorities, waiting for new designs, or (like you said) they could be building modules outside from view to quickly assemble them once they are ready? It might be a bit of all of these things.
Once the Chinese put into service all the ships they have launched already they should have as many major surface combatants, other than carriers, as 50% of the entire US Navy fleet. They will also have a huge amount of LPD craft. Expanding their Navy further than that makes no sense unless the PLAN seeks to expand their presence around the world much more than what they are doing right now.