I read some confusion information on the forum:
There's a thread which says unRAID does not have optical drive drivers and thus will never support passing through
There's another thread which says it's possible using "by-id" (which I can see on my rig e.g lrwxrwxrwx 1 root root 9 Apr 22 21:40 ata-PIONEER_BD-RW_BDR-207D -> ../../sr0) but then it refers to XEN, not KVM, I think.
Someone also said the only way is to passthrough optical drive is the entire sata controller.
Confused.
Using the similar code as above, without the recommended changes, I was able to see one SCSI Controller in Windows but I couldn't add the Virtio driver for it. After adding the controller code, removing managed='no' from <hostdev>, and adding address controller='1', I was able to see two SCSI Controllers in Windows and able to add the Virtio driver for one of them which allowed me to see the DVD drive!!
Removing managed='no' is probably unnecessary as it gets added back but n