udisksctl power off wrong disk

Question

I try to safely eject my external disk with the following 2 commands:

udisksctl unmount -b /dev/sdc1
udisksctl power-off -b /dev/sdc

The partition is correctly unmounted, but the second command gives the following error:

Error powering off drive: The drive in use: Device /dev/sdb1 is mounted (udisks-error-quark, 14)

Yes, I have another partition on another drive mounted /dev/sdb. But I want to power-off /dev/sdc. How is this supposed to happen? How can I remove safely sdc?

Ubuntu 20.04

(base) home@home:~$ lsblk --topology --exclude 7
NAME                      ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED       RQ-SIZE  RA WSAME
sda                               0   4096      0    4096     512    1 mq-deadline      64 128    0B
├─sda1                            0   4096      0    4096     512    1 mq-deadline      64 128    0B
├─sda2                            0   4096      0    4096     512    1 mq-deadline      64 128    0B
└─sda3                            0   4096      0    4096     512    1 mq-deadline      64 128    0B
  └─ubuntu--vg-ubuntu--lv         0   4096      0    4096     512    1                 128 128    0B
sdb                               0   4096      0    4096     512    1 mq-deadline       2 128    0B
└─sdb1                            0   4096      0    4096     512    1 mq-deadline       2 128    0B
sdc                               0   4096      0    4096     512    1 mq-deadline       2 128    0B
├─sdc1                         3072   4096      0    4096     512    1 mq-deadline       2 128    0B
└─sdc2                            0   4096      0    4096     512    1 mq-deadline       2 128    0B
sr0                               0    512      0     512     512    1 mq-deadline      64 128    0B

Thanks