My Fanxiang S910PRO 2TB speed tanks during the Splinter Cell Remake update because the SLC cache fills up. How do I stop this?

It's a joke—a drive marketed as PCIe 5.0 dropped to 800MB/s after writing 200GB of data. The Fanxiang S910PRO 2TB has a decent cache, but once that SLC buffer is gone, the native TLC speeds hover around a miserable 600-900MB/s, making the update progress bar move like a snail. I tried enabling 'write acceleration' in the software, but that was just a placebo; the write curve still took a nosedive after 15 minutes. I felt totally cheated by the marketing specs. To fix it, I manually left 200GB of unallocated space to force the controller to expand the SLC cache pool. In ATTO Disk Benchmark, the 500GB continuous write fluctuation narrowed from 800-5000MB/s down to a steady 3200-4100MB/s. I tried 100GB first, but it didn't really move the needle until I bumped it to 200GB. The drive ran hot, between 65-72℃, with the heatsink fan pinned at max. I used the config tool to back up this over-provisioning setup.