Why do I have micro-stutters in Need for Speed despite having 90 FPS?

While racing, I cautiously noticed that although I had 90 FPS, there were micro-stutters every few seconds, like a movie dropping frames. I tried closing all background programs, which lowered RAM usage but didn't stop the stutters, proving simple cleanup can't fix scheduling latency. I used the GamePP Resource Scheduler to lock CPU affinity to high-performance cores. FrameView showed frame time converged to 8-12ms, CPU temp stayed 68-75℃ per AIDA64, and fans ran at 1400-1600RPM.