A residual flow is f(z) = z + g(z). If g has Lipschitz constant κ, the reverse triangle inequality pins every stretch into the band (1−κ) ≤ ‖Δf‖/‖Δz‖ ≤ (1+κ): so ℓ = 1−κ, L = 1+κ. While κ<1 the lower rail 1−κ is positive — the grid warps but never folds, the map is invertible (Banach fixed-point), and you have bi-Lipschitz for free. Push κ≥1 and the lower rail hits 0: red folds appear where the grid turns inside-out, det J ≤ 0, invertibility is gone. It's bi-Lipschitz for exactly the same reason the latent rollout was stable — Lipschitz below 1. The contraction condition shows up a third time.