The semantic-boundary layer is proposed because high semantic proximity can be useful for discovery while remaining dangerous for interpretation. A system may retrieve two close concepts and still be forbidden to merge them.
Separation rules
Semantic proximity does not imply conceptual equivalence. Conceptual equivalence does not imply causal relevance. Causal relevance does not imply proof. Proof does not imply recommendation. Recommendation does not imply authorization.
False-neighbor discipline
A close but non-equivalent concept must be declared, not silently absorbed. The correct behavior is distinction, clarification, or non-merge. This layer is therefore adjacent to CCL, but not part of CCL.