You actually have a good point. I have in fact suspected it might be the game optimization app in the background to limit my thermals to 71°C. I should test that, but if it doesn't turn out to be the case, it's nothing ykk shouldn't be able to fix. It should be a table with all the thermal thresholds, somewhere in the system files.
However I suspect the game optimization app is the one at fault for GPU frequencies going down, and not the thermals. Because in benchmarks the GPU boosts up to 572MHz just fine (the game launcher isn't executed on the background). However once 70°C are reached, CPU throttles anyways. So it's a problem on both parts.
I'd gladly uninstall Game Booster, but it's a system app so I am afraid of removing it. Not to mention that force stopping it and removing its system modification privileges just don't help. It turns itself back on and it might be exactly what is ruining performance. I have no idea what to do. Perhaps Ykk can do something at Kernel level to disable that nuisance or at least bypass it. It just isn't good at what it is supposed to do. Game Optimizer App is also a problem, as it openly states that "It modifies maximum CPU/GPU clocks".