It was for the Parity Build speed, but to update, it turns out that my Parity drive was DOA and was failing as it was going. I now have a SMART failure report showing the drive as failed and the bad sector count over 450 so I returning my Parity drive. All my other drives have passed the preclear.sh script so should be good.
Thanks again for all the help, I am learning a ton by building this box.