One problem with these writers, is when they use the same terms to describe completely different concepts. Another problem is when they use different terms for the same things.
Matrix Signature is the same thing as Resonance Signature. It doesn't have anything to do with GOD or Convergence. It's a mark left behind by Resonance beings, only visible to other Resonance beings. But there are such thing as Corp Spider TMs, and they will notice your fingerprints left behind at a crime scene.
For whatever reason, they decided to make Erase Signature an Attack based Matrix action instead of a Resonance action like all the rest. Which means you risk OS for performing it, and risk taking damage if you fail the check.