>Now you might be thinking OPE is only useful if you have Facebook-level quantities of data. Luckily that’s not true. If you have enough data to A/B test policies with statistical significance, you probably have more than enough data to evaluate them offline.

Isn't there a multiple comparisons problem here? If you have enough data to do single A/B test, how can you do a hundred historical comparisons and still have the same p value?