For d>=3 external ports, use a connected acyclic tree of three-port equality tensors. It has d-2 internal vertices and d-3 internal wires; for d=3 a single vertex suffices. Splitting one external port through a new three-port vertex adds one external port, proving the counts inductively. Equalities force every connected wire to share the same value. Each all-zero or all-one external assignment has exactly one extension to internal wires; every other external assignment has none. Thus the replacement preserves the local equality function without adding multiplicity, while keeping internal degree three.