In my understanding cache only should be working as you said, but not really. And also mover settings are not so flexible, in my opinion there should be some more flexibility to use it, but again, i am not that experienced user, so i can be wrong.
Appdata is cache only, nothing on the array
My spin down delay set to 15 min, but once drives start they never stop. I know few of them not in use, but still they spinning
fortress-diagnostics-20210122-1316.zip