Standard BBN predicts the helium plateau at Y_p = 0.247 nearly parameter-free, and EMPRESS's extremely metal-poor anchors now measure 0.2370 +/- 0.0034 (2022, 3σ low), with the 29-galaxy follow-up at 0.2402 +/- 0.0040 (2025). The cleanest fix, an electron-neutrino lepton asymmetry of xi_e near 0.05, imports an asymmetry orders beyond the baryonic one with no mechanism; the alternative is systematics in the least forgiving element.
Helium is the model's rigid element: with eta fixed by the CMB and standard neutrino physics, Y_p has no freedom, so a low plateau forces either first-second new physics in the neutrino sector or an indictment of the measurement chain. The model cannot shade the prediction; it can only choose which crisis.
SCT stands in the same line of fire by design: cascade termination before one second (P40) hands nucleosynthesis to standard equilibrium physics (P42), so the framework predicts the standard plateau, Y_p = 0.2449 +/- 0.0040 in the canonical ledger, and a confirmed EMPRESS-level shift would strain SCT exactly as it strains ΛCDM. No SCT mechanism is invoked to absorb the anomaly, and pretending otherwise would violate the framework's own equivalence theorem: the registered prediction is that the abundances match standard BBN, with deviation beyond 2σ flagged as a kill condition on the cascade-termination timeline.
What SCT contributes is the diagnosis hierarchy. The framework's derived baryon sector (R_b from cascade geometry, agreeing at 0.17σ with observation) and its identical-BBN structure make a genuine helium deficit attack the shared foundation, not an SCT-specific layer, while the cascade offers one bounded caveat: non-equilibrium corners of the multi-phase sequence (P45) could in principle perturb yields, but P40's termination constraints render this inactive at the measured precision, so SCT's honest position is to back the systematics investigation, where the helium emissivity and extrapolation chains carry known fragilities, and to await the 30-meter-class anchors.
This is the same epistemic stance as the lithium problem: shared open problems are declared, not absorbed. There is no need to invent a mechanism for an anomaly that may not survive its own error budget.
The registered kill is explicit and shared: a confirmed primordial Y_p deviating from the standard prediction by more than 2σ after systematics are settled would falsify the cascade-termination timeline that makes SCT's BBN standard, forcing either a revision of the termination epoch or the framework's abundance sector. SCT carries no lepton-asymmetry escape: the EMPRESS plateau, if it hardens, is jeopardy SCT has chosen to share.