Due to some “makeover” work for Disk Utility in El Capitan, the GUI version of Disk Utility did indeed have the features for RAID management (including creation of Software RAIDs) altered and reduced. I’m not sure exactly what is meant by this rather vague statement, but if the allusion is to MacOS’s ability to create a software RAID, this is not only out dated info, but was only ever half true to begin with. Using OWC's SoftRaid to give back RAID support that was stripped from macOS