My two cents here. The Moravians kept great records and I find it certainly possible that Cornelius' father, William could have married a SCHELL/SHELL.
After the Revolutionary War, Cornelius was a brick mason and grist miller as well as a planter. He appears to have done a lot of brick work for the Moravian community in Wilkes County (Moravian papers) He and his brother, Leonard Sale, appear frequently in the court records, land records, etc. They served on the grand jury, were appointed to various committies and were overseers of road repairs. Not solide evidence but the connection was there.