Not Really. It actually comes from eliminating the egr probe that the catless up-pipes don't have a provision for. A cel fix can be used on the egr probe.
I didn't say the cel can't be eliminated. I think you mean EGT probe. Yes, not having it in use will throw a cel. Also, some cat-less up-pipes DO come with the egt bung and if one decides to use their egt sensor without the cat, it will throw an exhaust gas temperature circuit malfunction code.