QA vs S4.

The generally accepted difference is that QA is proactive, while QC is reactive. QA is typically proactive, focusing on establishing processes and procedures to prevent issues before they occur. 
QC is more reactive, involving activities that detect and correct issues in the product or service life cycle. 
We consider the settings as a QC as it is the result of a QA. (ie supplier accountability, condition check which are proactive quality orders.)