If it's one race that changes wet to dry or vice versa, then there can be no change of setup. With 1 dry race and 1 wet, the setups will be different, which will affect lap times.
And you would have to take averages, to minimise minor variations. Averages over a sufficiently large number of races, any AI OP will clearly show.
Highly impractical, but theoretically best way to show any discrepancy.