HDDs don't suspend on schedule

I’m using Gnome Disks to configure power management for my HDDs. The partitions of this one HDD are not mounted and I’ve set it to suspend the drive after 20 minutes.

But even after hours of uptime, the disk doesn’t go into sleep mode. It does, if I tell it to go to sleep immediately through Disks, and it even works as expected on the Ubuntu 18.04 installation I also have on the same PC.

So what’s wrong with Fedora 32 here?