Why does saving stutter in MGS5 Definitive Edition?

Saving in MGS5's open world caused painful stuttering, with write latency hitting 12-15ms on my Intel 545S 2TB. I tried cleaning junk files, which freed space but did nothing for write speed. I used GamePP Storage Queue Depth Configuration to raise queue depth to 128 and enable forced write cache refresh. CrystalDiskMark confirmed sequential write speed increased from 500MB/s to 540MB/s, and AIDA64 showed drive temperature stable at 45-50℃. The saves are now instant and the game flows perfectly.