I think the term "combined mode" in SATA IDE Combined Mode is causing your question.
Combined in SATA IDE Combined Mode does not refer to combining multiple drives into a RAID array. Combined means the SATA ports can be used with both SATA drives, and IDE with PATA drives that use the older ribbon cables, or an IDE/PATA to SATA adapter. That option is an old compatibility option that is not compatible with RAID, as the warning you included confirms.
Just disable SATA IDE Combined Mode, and use RAID mode and it will work fine.