Interesting. I am using that same strategy (virtual LSI SAS to get SMART) to connect to NVMe drives via physical RDM, on DSM 6.1.7 and DS3615. I don't see any reason one could not attached SAS drives via physical RDM and do the same.
On 6.2.x, 1.03b and DS3615, this does not work unless the storage pool is built first using a virtual SATA controller, then go back to the VM config and move the drives to the virtual LSI SAS controller. I"m not sure if that would work with your SAS drives via RDM, but I suspect it may.
Your post however caused me to edit the original "please Jun" request to be agnostic vs. 3615 or 3617. Obviously if one or the other will be supported, the latest hardware would be a better choice at this point.