In shared‑genome language‑model societies, restricted evidence visibility encourages the use of reusable, value‑indexed latent packet interfaces, while the sole high‑performing globally visible model in the parent study learned an episode‑entangled code.\ \ This companion work asks two questions: do independently trained societies share a single packet language (strict zero‑shot transfer fails), and does inherited interface state help or hinder later learning?\ \ First, a leakage‑controlled causal interoperability audit was performed over all 30 ordered pairs of six independently trained restricted societies, using sealed held‑out structure and a preregistered raw/orthogonal/linear/nonlinear alignment ladder. The six semantically similar interfaces do not form one raw language: only one same‑initialization pair is fully interoperable in both directions; a second pair shows asymmetric partial compatibility; and the remaining 26 cross‑initialization directions fail at every frozen alignment rung.\ \ Second, within the tested decomposition and a single sealed source formulation, a source‑span control localizes strict zero‑shot failure to the interpretation and execution of new operator instructions.\ \ Third, in a matched adaptation factorial, the globally trained communication interface acts as a severe negative‑transfer prior: reinitializing only the packet reader, writer, and mouth raises final depth‑three accuracy from 0.169 to 0.857.\ \ Fourth, across two restricted checkpoints and two independently frozen target streams each, inherited interfaces never exceeded fresh‑interface controls by the preregistered 0.10 margin.\ \ All primary conclusions are bounded to a near‑transfer 17‑state setting; the negative‑transfer factorial concerns the single globally visible parent‑cohort checkpoint, and an appendix adds a post‑hoc tagged‑global twin case study.\ \ Review