Spin down of Icy Box Raid Enclosure not working

I am running Ubuntu server 18.04 and I am using an ICY BOX IB-RD2253-U31 enclosure with two WD Black disks (no NAS disks) in RAID 1 mode (mirror).
The external enclosure is connected via USB to the Linux server. The disks are two 1TB Western Digital Black disks, connected via SATA inside the enclosure (S-ATA 6.0 Gbit/s (S-ATA 3)).

I want to put the two disks in sleep mode / spin them down with hdparm (lowest power consumption sleep mode) with sudo hdparm -Y /dev/sdb but the disks seem to run like nothing happened. I also tried sudo udisksctl power-off -b /dev/sdb: This causes the OS to eject the drives, but the disks are still running (I can hear them running, and a small click when shutting it off with the built-in power switch).

Is this the fault of the enclosure? And is there any way to spin down the disks completely until needed again?

Answer

Attribution
Source : Link , Question Author : JJ Abrams , Answer Author : Gernot