Skeptical here as well, no one is proposing a serious mechanism for damage like "you left gate oxide uncovered by silicide so it contaminates the CMP machine" o

Skeptical here as well, no one is proposing a serious mechanism for damage like "you left gate oxide uncovered by silicide so it contaminates the CMP machine" or whatever. What I can imagine, is that the foundry only tests their magic OPC algorithm with DRC clean inputs. If your mask isn't DRC clean, who knows what's coming out the other side.