Hrmm. Still guessing about your workloads, but isn't it possible that workload A could cause a disproportionate amount of amplification, while still being much smaller in aggregate than workload B?

Seems possible, though we only incorporated FDP changes to the non-rocks writes and saw large WAF reduction. (We're approximately an object store as a service with rocksdb for metadata and direct disk writes for data; typical object size is hundreds of kB to single-digit MBs, and rocks updates are batched. Many of our users can accurately predict how long their objects will live, so we can segregate FDP streams by lifetime.)