ACT gravity mediator witness

Answer
YES for the mediator-only witness run.
NO for a purely classical mediator model under the same mediator-only conditions.

Reason Why
The positive run assumes locality and interoperability, excludes direct coupling between the two quantum systems, and records an entanglement witness after interaction through the mediator alone. Under those constructor-theoretic conditions, the mediator must be non-classical, so the run rules out a purely classical mediator model. The contrast run keeps the same locality, interoperability, and mediator-only structure but assigns the mediator a purely classical model. In that case the mediator-only entanglement witness is blocked, so the run cannot support the same non-classicality conclusion.

Check
C1  OK - locality is assumed in the positive run
C2  OK - interoperability is assumed in the positive run
C3  OK - direct coupling between the two quantum systems is excluded
C4  OK - the positive run has a mediator-only interaction path
C5  OK - an entanglement witness is observed in the positive run
C6  OK - the positive run supports an information-transfer interface
C7  OK - the positive run supports local readout
C8  OK - the positive mediator is derived to be non-classical
C9  OK - a purely classical mediator model is ruled out by the positive run
C10 OK - the non-classicality conclusion applies to the gravitational mediator
C11 OK - the contrast run is also mediator-only
C12 OK - the contrast run cannot support a mediator-only entanglement witness
C13 OK - the purely classical gravitational mediator cannot mediate entanglement under the witness conditions
C14 OK - the contrast run cannot support the non-classicality conclusion