Why does my Vastarmor RX 9070 XT drop FPS in MGS V?

While infiltrating the enemy base, I watched the frame rate table and saw the 9070 XT frequency fluctuating wildly between 2.1-2.6GHz. FPS jumped between 144 and 90. I first tried disabling Radeon Boost in the drivers; while fluctuations decreased, the overall FPS ceiling dropped by 10, making me hesitant about this sacrifice. I used the GamePP Fan Curve Configuration Panel to set speeds to 85% above 70℃ and locked the core frequency. Frame generation time stabilized at 6-8ms per FrameView, and core temperature stayed at 72-77℃ per HWiNFO. Now I verify