After reading this thread, I should have realized that just testing it was the best way to know.
In case it's useful, I'm on Unraid 6.8.3 using Unassigned Devices + ZFS with my SAS drives, no SAS drives in Unraid array.
I ran "sg_start -r --pc=3 /dev/sdb" last night, waited a bit and ran
# sdparm --command=sense /dev/sdX
/dev/sdX: SEAGATE ST33000650SS 0003
Didn't look like the spin-down occurred. I didn't see anything in System logs with SAS Assist, spin down
Checked system log again this morning and nothing new, but the drive did spin down (gray balled) and I get the below when I checked this morning
# sdparm --command=sense /dev/sdb
open error: /dev/sdb [read only]: No such file or directory
# sg_start -r --pc=0 /dev/sdbsas-util-out
sg_start failed: No such file or directory
So, the drive did spin down sometime last night, but spin-up failed and I didn't see anything in system logs.
EDIT: I restarted my computer (after re-attaching all the cables) and the drive successfully came back online
"/usr/local/emhttp/plugins/sas-spindown/sas-util test" output attached, matches my findings that spin-down request wasn't followed