Helium-4 carries the cleanest theory in cosmology, Y_p = 0.247 from known first-second physics with sub-half-percent uncertainty, and the messiest precision measurement: EMPRESS anchors pull toward 0.237 to 0.240 while Izotov-Thuan samples and CMB damping-tail constraints sit at the standard value, a spread among methods exceeding the individual error bars. The element that should arbitrate the first second is itself awaiting arbitration.
The model leans on helium as its rigid first-second anchor: N_eff bounds, lepton asymmetry limits, and injection constraints all inherit the adopted Y_p. With determinations split beyond their errors, every such constraint quietly carries a measurement choice, and the model has no internal way to pick the true plateau.
SCT's helium position is structural identity: the cascade terminates before one second (P40), weak freeze-out proceeds in equilibrium (P42), and the framework's registered prediction is the standard Y_p = 0.2449 +/- 0.0040 with no SCT-specific shading (P29, P30 carry the yields forward untouched). The framework therefore reads the present spread as measurement systematics until proven otherwise, and stakes itself on that reading: helium is one of the three constraints (with the deuterium abundance and FIRAS spectral purity) that anchor the cascade-termination timeline itself, so SCT cannot shop among determinations any more than ΛCDM can.
What the framework adds is the cross-anchor structure: SCT's first second is additionally constrained by the derived baryon loading (R_b at 0.17σ from observation) and the cascade-geometry N_eff = 2.514, so the helium plateau, when settled, lands in a web of derived first-second numbers rather than a single fitted one. A standard plateau confirms the termination timeline; a genuinely low plateau strains it in a declared, quantified way, while also pressing the ΛCDM N_eff sector, since the same Y_p shift that suggests lepton asymmetry shifts the inferred radiation density toward SCT's lower derived value.
This is the same shared-jeopardy stance as the plateau-shift entry, held at the level of the element itself. There is no need to adjudicate the dwarf-galaxy emission physics from the armchair; the framework declares what each outcome costs.
The registered kill: a settled primordial Y_p deviating from 0.2449 by more than 2σ falsifies the cascade-termination timeline that makes SCT's nucleosynthesis standard. The cross-anchor adds a second blade: helium and N_eff must move consistently under the cascade structure, so a settled standard Y_p alongside a CMB-S4 N_eff at 3.046 (against the derived 2.514) would also break the first-second geometry, from the radiation side.