They just do more trials if they want to be assured of reliability, and other docks in the shipyard are more convenient for that function. And for continuous testing, that should be better done in the fitting docks. The dock the two 052Ds seems like a dock to moor finished ships awaiting delivery and their paper work. In fact, I think the Type 055 near that building was moved later to a dry dock, because that place near the building isn't conducive for fitting either, and being moored there was planned to be temporary all along. The other Type 055 and the Type 052D in the right continued to remain in those positions as these are the proper fitting areas.
As for the batches, the first two from Dalian, which are the two ships on the left, docked near the building, are from the earlier batch --- booms on the Type 346A radar, Type 730 CIWS, are the giveaways.
The Type 052D on the right on the other hand on the fitting docks, is the new batch, featuring radars without the booms (the wiper like things underneath the array), the Type 1130 CIWS, and a revised ESM on top of the bridge.
Its possible the Dalian first batch 052Ds had delays, as they were in this situation when Jiangnan's second batch (Type 1130, wiperless arrays) were already being commissioned.
