II. Cylinder collision, bit non-reuse and effective non-degeneracy in the 2-adic Collatz dynamics

This paper proves the effective non-degeneracy conjecture formulated in the author’s previous study on the 2-adic structure of the compressed Collatz dynamics 10.5281/zenodo.18685581. It establishes that the restricted survival sets inside a fixed modular class decrease exactly by a factor of one half at each step. The proof relies on the precise cylindrical structure of the 2-adic valuation levels, the affine behavior of the dynamics within each branch, and a structural separation argument based on cumulative 2-adic depth. It is shown that distinct itineraries cannot collide at any finite resolution, ensuring injectivity of the correspondence between admissible trajectories and initial residues. As a consequence, the infinite survival set has Haar measure zero. The question of its emptiness, which is equivalent to the classical Collatz conjecture in the principal modular class, remains open. Version 1.1: Maintenance update including minor revisions and the resolution of issues identified in the previous version. This paper is part of a series of six works on the Collatz conjecture. In reading order: I. 2-adic structure of tails and survival sets in Collatz dynamics https://doi.org/10.5281/zenodo.18831439 II. Cylinder collision, bit non-reusage, and effective non-degeneration in 2-adic Collatz dynamics https://doi.org/10.5281/zenodo.18831527 III. Arithmetic obstruction to indefinite survival in 2-adic Collatz dynamics https://doi.org/10.5281/zenodo.18831690 IV. Arithmetic obstruction to mixed orbits in 2-adic Collatz dynamics https://doi.org/10.5281/zenodo.18831791 V. The ϕ function and the extension of the 2-adic budget argument to arbitrary k0 in Collatz dynamics https://doi.org/10.5281/zenodo.18831874 VI. Structural reduction of the Collatz conjecture: stretches, portals, and 2-adic survival sets https://doi.org/10.5281/zenodo.18831607