Why does my frame rate drop under extreme load in A Plague Tale: Requiem?

I was cautiously observing my performance in A Plague Tale: Requiem when the frame rate dropped from 60 to 45 FPS. The Onda 9D4-VH-D was clearly thermal throttling. I first tried fixing the fan speed to 100%, but the noise was unbearable and performance didn't improve. I then used the GamePP Power Plan Switcher to enable High Performance. In the GamePP Fan Curve Configuration Panel, I re-drew the curve to hit 80% speed at 75℃. HWiNFO showed the temperature stabilizing at 72-75℃. The frame rate fluctuation converged to 58-62 FPS. 3DMark stress tests verified the cooling efficiency. The system is now stable, and I can verify my performance without worrying about heat spikes.