Hi C,
Interesting answer. My limited knowledge indicates that JBOD systems require XHCI implementation so that a number of devices and a number of data streams are viable over one USB 3 port. It also appears that current PC hardware comes with this as a default, but Macs don't, although further research tells me that Apple have implemented the same system as found in PCs but with an arbitrary limit to the number of devices supported.
Further, RAID systems have no such need as they don't have any requirement for identifying the multiple disk devices over the USB connection.
Furthermore, the only manufacturer you mentioned available in Australia is OWC, and the price is quite high. Apple offer one box at an excruciating price, and the other options include ICY BOX and Orico. Interesting that the manufacturer I got the statement about XHCI from has disappeared, and their products are no longer listed by retailers.
There is a glimmer of hope regarding the ICY BOX IB3640SU3, as one of my retailers actually describes JBOD functionality in detail and states Apple compatible too. I have contacted them with specific questions and confirmation that it will work with my iMac.
More when and if they get back to me.
Foggy