Eh??
The only reason they chose not to write drivers was that it wasn't on the Hyperion roadmap. (Certainly wasn't a technical reason for most hardware) Classic support was only supposed to be a stepping stone to the Amiga-One so why write drivers for exotic hardware they didn't own?
As for what Kin-Hell wrote about memory.. I think it's bollox. There is absolutely no reason to support motherboard SCSI in OS4!
Why not??
You need a CSPPC for OS4 on A3k/A4kT and so automatically get a much, much faster UW-SCSI3 controller! Instantly making the motherboard SCSI redundant. (If the CSPPC SCSI isn't supported under OS4, then my argument doesn't hold!)
I think the reason there is no Blizzard SCSI support is that if you remember OS4 wasn't destined for that platform until very late in the day. Laziness coupled with economics is why there are no drivers.