Why do I get micro-stutters during Ghost of Tsushima combat?

Galloping across Tsushima was great until massive combat effects triggered sudden stutters. I first tried lowering texture quality to Low, but the visuals became blurry and the stutters remained, which made me really anxious. I then accessed the GamePP Resource Scheduler, set the game's disk priority to Real-time, and killed background sync. RTSS monitoring showed frame times finally converging to 11.8-14.5ms. I also tracked 46-53℃ temps via AIDA64 and saw I/O wait times drop to 10-26ms using the GamePP Frame Time Analyzer.