If enter the following commands on the command line it works as expected and spins down in the specified time.
sudo hdparm -S 120 /dev/sda
sudo hdparm -S 120 /dev/sdb
Putting this in /etc/hdparm.conf does nothing however. The disks just stay spun up indefinitely.
command_line {
hdparm -S 120 /dev/sda
hdparm -S 120 /dev/sdb
}
I'm running Ubuntu Server 16.04.2