Perelman’s resolution of the Poincaré Conjecture shows that any closed, simply connected three-dimensional manifold is topologically equivalent to the 3-sphere (S³). This paper asks a different question: given the specific transport rules of Holosphere Theory—triadic spin couplings, spin-½ behavior with a 4π monodromy, a bi-invariant small-strain transport law, a surface-scaling “vacancy” relation, and a photonic coherence gate at ε_crit = 2α—can any compact three-manifold other than S³ support long-range, self-consistent coherence? We formalize this as the Coherence–Forced Uniqueness (CFU) principle and prove that, under these assumptions, only S³ (equivalently SU(2)) satisfies all four coherence axioms. Manifolds such as S²×S¹ and lens spaces L(p,q) are shown to fail at least one of the spinor, triad-closure, or holography requirements. On the computational side, we implement a shared CFU simulation harness and key performance indicators (KPIs) that operationalize the theory: spinor monodromy (KPI–A), triad closure (KPI–B), commutation of transport and smoothing (KPI–C), vacancy shell law (KPI–D), and energy/entropy bounds (KPI–E). As an initial commissioning test, we run the harness on S³ and S²×S¹ with identical small-strain and gating parameters. For S³, the global shell fit matches the expected R² ≈ 0.9982, spinor monodromy residuals are on the order of 10⁻⁶ for both 2π and 4π loops, and a directional cap of half-angle 0.6 radians retains a high-quality shell fit (R² ≈ 0.9957) with more than 20,000 nodes. Under the same configuration, the corresponding cap on S²×S¹ contains only 68 nodes and does not support a stable shell fit, indicating that the product manifold is already structurally stressed by the CFU gating and directional constraints. These results do not yet constitute a full numerical proof of CFU, but they show that (1) the S³ implementation behaves exactly as predicted by the analytic framework, and (2) directional and path-structured KPIs begin to discriminate between S³ and non-simply-connected competitors even in a minimal run. A planned five-paper CFU/Poincaré series will extend this work to full KPI grids on lens spaces and other carriers, as well as to laboratory and astrophysical tests.