RAID unsupported?

I have been reading around the Acronis website that RAID disks are unsupported... in what way?

I have an OWC Mercury Elite-AL Pro Qx2 with a striped and spanned set of 4x 2TB drives, and a Drobo 5D with a set of 4x 4TB drives and dual-failure protection enabled. One is currently designated "Working RAID" and the other "Archive RAID" (all for my employers large photo library). I have not yet tried backing up one RAID to the other, but I did schedule a backup of the System volume to the Archive RAID... and it SEEMS to have worked, but given the nature of Mac software to hide useful information and provide little real control, I'm not sure if it actually did (no Validation option, no email notification options, etc).

Can you please clarify in what ways RAID is not supported? Thanks.