framesWithheldFor method
Whether a row in state is one whose frames this report chose not to
carry.
The question a stage has to ask before it says a side drew nothing: on a findings-only export an unchanged row has no frames beside the file and had two perfectly good ones on the machine that ran it.
Implementation
bool framesWithheldFor(ComparedState state) =>
exported == ExportedFrames.findings && !isComparedFinding(state);