From@adamuk01, who will be able to correct me for this first Weka GitHub issue!

It is possible to obtain per-object-store metrics (e.g. amount of data uploaded/downloaded) for tiering. However, it is not possible to obtain this data per file system.

This could be generated by collating per-object upload/download metrics, and would give a better idea of total utilisation of each file system and NVMe tier hits/misses for further policy tuning as appropriate.