"Addendum: Two-Parameter Base-Change Invariance and Polysector Independence for I16 (Δ_Z)"

This note records the two-parameter invariance conditions needed for canonicity of the I16 boundary data for normal-crossings degenerations over a bidisk. It states: (i) existence and polysector/path independence of the renormalized curvature complement-block limit under a tameness premise (bounded holomorphic family on polysectors after the prescribed renormalization), and (ii) invariance under two-variable branched base change (t1,t2) = (s1^(m1), s2^(m2)). No new constructions are introduced; the purpose is to make explicit the invariance requirements used in multi-parameter verification.