ϒ = true scatter / quoted width — is the error bar honest? · Ξ = quoted width / exact-analysis width — was all the information used? Honest data cannot beat the exact analysis: ϒ·Ξ ≥ 1.
Sliders stop at the information bound ϒ·Ξ = 1. “Systematic part” turns scatter into a fixed offset of every estimate.