Take a window length k equals 2 for concreteness, though the argument does not need smallness. Let F be any function of two inputs. Let n be 3-bad, so the first three valuations are one. Then the window at n is (1, 1). After one Syracuse step, the window at C(n) is (nu_1, nu_2) which is again (1, 1). F sees the same pair. Subtracting F cannot create a decrease. The log term increases by more than log of three over two because an expanding step grew the odd part.
Now lengthen the flashlight to k equals 8 because it feels safer. The adversary chooses a 9-bad n. The window of eight ones slides by one step and remains eight ones. Same cancellation. The feeling of safety was a feeling about your beam, not a fact about the hallway.
Replace linear F with a neural net over the window if you want to be theatrical. On the all-ones window the net outputs some number c. After the step it outputs the same c. Theater cancels. This is why the strengthening matters psychologically. It blocks the escape hatch that says my two coefficients were too primitive.
Replace F with a function that tries to special-case the all-ones tuple. It still outputs a single number for that tuple. Before and after, same tuple, same number. Special casing the villain signature does not help when the signature is stable along the step that breaks you.
That stability is the geometric content. L-bad streaks are not only bad because they expand. They are bad for look-ahead certificates because they look like themselves under a shift until the streak ends. Fixed windows are shift-local. Shift-local scores are blind on long constant streaks.
Residue certificates fail for a related geographic reason with a different mechanism: congruence information near minus one cannot manufacture enough descent reward when the dynamics force expansion. I am not restating Hsieh's proofs here. I am marking the kinship and the difference. Kinship: minus-one neighborhood. Difference: residue ansatz versus look-ahead-window ansatz.
If a future ansatz wants to survive, it must either change window length with n in a controlled way, or reach outside pure finite look-ahead of nu's, or accept that it only certifies a subclass and say so. Subclass theorems can be honorable. Quietly claiming a subclass certificate as a universal Lyapunov function is how we got here.
End of the slow example. If it felt repetitive, good. Repetition is the pedagogic form of cancellation. The math is repeating ones. The mistake is believing a new costume changes the ones.