Connecting hard drives to storage space direct 2016?

Question

Windows Server

Who faced tell me!
As you know from the step-by-step manual in the trial version of WinServer2016 TP5, you can already implement storage space direct. Thus, connecting the local hard disks to the pool. Seems like a great budget solution.
But as practice failed, only hard drives connected directly to the motherboard via the sata connector are seen. A basket with sata hard drives connected to a raid controller via a sas expander is no longer visible and cannot be used in storage space direct (even in jbod mode).
Then what is the point of such technology?
Personally, I wanted to install 2 not very powerful servers, stuff them with 4-6Tb sata disks, connect everything with one SAS expander and give it to the operating system as jbod. After that, organize StorageSpaceDirect and store not very demanding Hyper-V VMs there, knowing that there is a mirror.
How then to connect to 1 mat. board up to 12-16 hard drives directly?