Are we sure this is a new boat, rather than merely an older one having undergone a refit?
Specifically, the sail is not the newer "blended" type seen on recent new build 039As, but rather the older kind...
edit: yep, that particular sub definitely follows the older type design rather than the new one, a good comparison pic below:
We can see that the newer 039B (sometimes called 039C) on the left of that picture has a sail which is blended anteriorly, but also has a different shaped "cutout" on the aft of the sail compared to the older 039A. The 039B also doesn't have the two anterior "boxes" on the sides of the sail, whereas the older 039A does.
The pattern of drainage holes also differ a little, but the biggest differences are on the sail.
The Yuan in the pictures you post I think are definitely the older 039A type rather than 039B, so I suspect the submarine is probably an 039A that had been refit or under the process of going to be refit... unless the shipbuilders have decided to opt to build older 039As instead of 039Bs for some reason, but that is unlikely given multiple 039Bs have already been produced and if any design problem were present it should have been discovered a long time ago.