hdparm.conf settings don't seem to run at boot

I'm trying to get my HDD to spin down after boot, as I only use it occasionally for backing up and long term storage. I'm running Ubuntu 17.10.

I've been searching for a while and found that I can edit the hdparm.conf file to include this:

command_line {sudo hdparm -S 1 /dev/disk/by-id/ata-ST2000DM006-2DM164_Z4ZAL35H}

I've also tried all sorts of variants of it, with indentation, without the "command_line" option, and instead just done:

/dev/disk/by-id/ata-ST2000DM006-2DM164_Z4ZAL35H {spindown_time 1}

None of it has worked so far.I have disabled "mount on boot" option for the drive.

The thing that confuses me the most, is that when I run

sudo hdparm -S 1 /dev/disk/by-id/ata-ST2000DM006-2DM164_Z4ZAL35H

the disk will spin down after 5 seconds, just like it is supposed to do.

So, is there any possibility that the hdparm-conf settings aren't applied at boot, and if so, how do I fix it?