Remark: Exactness and its boundary

This theorem uses a target-adapted substrate. It is not a claim that an arbitrary null displacement is exactly attained on one fixed lattice. En08-B instead supplies resource-controlled approximation for a prescribed null boundary on its declared lattice family CheungEn08B. Our construction has the same essential reference-preserving permutation identity, but a different spatial permission contract. No resource formula is transferred between these models.