How do you know what forces the particular 130 mm Mount transmit the the hull girder and what the hull was designed to absorb in the first place, and how much more it can be readily reinforced?The original comment is closest to the truth but it has nothing to do with shell velocity. The primary function of a muzzle brake is to reduce recoil but the key disadvantage is greatly increased noise to the sides and rear. Being a 7,500-ton platform, the 052D wasn't supposed to mount the 130 mm in the first place. So when they upgunned from the original 100 mm Type 210, it was logical to add a muzzle brake to reduce stress on the hull when firing. The Type 055 is a much heavier, wider, and sturdier platform and so doesn't need a muzzle brake to reduce recoil, with the added bonus of not shattering the eardrums of everyone on the bridge.
055’s gun is much farther from the bridge than 052’s, so the need to reduce lateral muzzle blast and noise is correspondingly less.
The gun mounts on 052D and 055 looks otherwise identical to me. I think the most likely the explanation for deletion of muzzle brake is simply that a few years of operating experience shows the muzzle brake to be unnecessary.
Another clearer image had come out at haohanfw site, indicated that 2 052D destroyers are being contructed in the dry dock.A clearer image. Still too blurry to judge. I'm not certain, but the module on the right seems too wide to be a 052D. Withholding judgement until further images or credible rumors.