Evaluation of the Einstein row

The theorem is an existential counterexample in the frozen admissible class, already at $m=0$. It does not assert a nonzero value for every mass, observation, switch, or parameter. One counterexample suffices to exclude the unrestricted invariance theorem.

The parameter space has not been shrunk. The field $D^{\ast }b$ is nonzero exactly where a nonconstant auxiliary field can be detected. The constant-$b$ zero check in Proposition prop:subclass remains consistent with the integration by parts.