selects on atm_iv's own trailing-year rank and measures atm_straddle: the two are formally different quantities, but not empirically different ones -- in the 7-45 DTE band this pattern selects on, period-over-period fractional change in atm_straddle correlates 0.876 with fractional change in atm_iv, because an ATM straddle's price at this tenor is dominated by vega exposure to implied volatility. Selecting on an unusually low atm_iv reading and then measuring atm_straddle's own subsequent change is therefore almost the same test as selecting on and measuring atm_iv itself: an unusually extreme value tends to be followed by a less extreme one purely by chance, so this design finds an apparent effect even in data with no relationship at all. Testing it honestly needs a null that reproduces that tendency, which this harness does not implement. Not tested -- not rejected on evidence.