......They definitely wouldn’t spend time trowelling.....
My Asian experience is different. I’ve seen the absolute worst formed concrete and concrete block work imagineable parged over and troweled smooth. I’ve seen many examples where they recreated the morter joints with tools in the freshly applied stucco to make it look like the concrete block construction they parged over.
As labor rates increase in China, much of that is going by the wayside. That being said, you might be right depending upon when these particular dams were built. Although it’s hard to believe such a large dam would use concrete blocks as we know them.
In 1987, My cousin, who was an engineer for the China Civil Engineering Construction Corporation (a quasi-government public works company), said the CCECC was about 20 years behind the times as far as the engineering profession. Even 20 years before that, the lateral force of that volume of water would require some interlocking and reinforced structure. Surprisingly, Chinese engineers were somehow getting Dutch, German and Canadian structural and civil engineering periodicals during the Cultural Revolution.