Makes sense. Sounds like with your level of understanding you’ll appreciate these photos and analysis, if you haven’t seen them:
https://www.taiwannews.com.tw/en/news/3965733
Good link - a little discussion to go with it. The 3G spillways all appear to be in the center section of the dam, with hydroelectric generation located on either side. The second image (from 2017), you can see a bit of evidence of the swirl of water just below the dam - this is likely caused by the generation running, with water going through the internals of the dam, including the turbines, and being discharged below the water level. I see similar at the local dams here in SE Tennessee (TVA dams).
The spilling of water does churn up the river downstream of the dam. During flooding in 2003 in Chattanooga, I visited near the Chickamauga Dam with all its spillways wide open. The river looked like Lake Erie on a windy fall day!
Notice that the spillway area is separated from the generation area - that is so that the turbulence caused by spilling water doesn’t interfere with the generation. Some nasty back pressures could develop and could damage the turbines otherwise.