Status: IN
The costs of zero-coupling isolation — tooling confusion, naming drift, convention divergence, duplicated definitions — are exclusively non-runtime phenomena; at execution time, duplication is free (every copy is independently correct) and isolation's side effects (misleading imports, stale aliases) never manifest.
Duplication carries zero maintenance cost when correct (depth-2) and isolation side-effects are invisible at runtime (depth-4); combining shows the isolation architecture has literally no runtime penalty
Depends on (SL): duplication-cost-free-when-implementations-correct, isolation-side-effects-invisible-at-runtime