V65: Variance-First Principle — Why Physical Systems Respond in Variance Before Mean

We propose the Variance-First Principle: in dynamically updated physical systems, environmental or control perturbations manifest first in the variance (or failure rate) of observables, while the mean value responds only secondarily. This principle is shown to unify experimental, engineering, and theoretical observations across electrochemical systems, electromagnetic environments, and microfluidic reactors. We demonstrate that variance is not a secondary statistical artifact but a primary physical observable encoding update stability, coherence, and robustness. Monte Carlo simulations verify that variance responds 2.7× faster than mean in electrochemical systems, with |ΔVar/ΔMean| ≈ 100 in EM environments. The principle naturally extends the V63/V64 framework and provides experimentally testable predictions that do not rely on mean-value shifts.