just because there is low demand does not mean automatically they will get naval order, have these shipyards made naval ships in the past>? do they have the expertise and infrastructure to construct these corvettes
if HP and HD make the Type 056, its hard to see a 3rd shipyard being set up for a construction of the same vessal, unless that is China really wants to up the tempo on these, which so far it hasnt done with neither Type 052C, Type 054A or Type 071
The more inland shipyards were responsible for the massive build up of 022s after the initial production by larger shipyards. The smaller inland shipyards could handle 022 because it was a relatively small ship. It's believed they can handle something along the lines of 056 by now.