This paper develops a general structural reclassification principlefor physical and mathematical quantities that have long been treatedas distinct, dynamical, or ontologically independent. Building on the projection–exclusion grammar established in v1.0and the combinatorial uniqueness result of v1.1,and on the observational two-tier separation introduced in v2.0,the present work formalizes a universal distinction between: (1) structure-level invariants, and (2) representation-level or observer-dependent quantities. The framework is developed entirely within the static (isotropic) regime.No physical time, dynamics, or new interaction is introduced.Instead, the work shows that many persistent tensions across physicsand mathematics arise from systematic misclassification betweeninvariant structures and their effective realizations. This reclassification principle is applied uniformly to: – running couplings and renormalization,– bulk–boundary asymmetry,– cosmological tensions,– gravitational interpretation problems,– and mathematical confusions between invariants and representations. A finite structural grammar (Q₄ with first-order cancellationand finite adjacency) is shown to be the minimal structurecompatible with observability. The result is not a modification of physical law,but a structural clarification of what type of quantityis being discussed in each context. This work corresponds to v2.1 of the series andprovides the universal classification layerthat prepares the transition to v3.0,where update order and irreversibility will be introduced.