OP acknowledges this... "Unfortunately, using the mean as a test statistic is flawed - it only works when the pre-selection distribution of A and B is identical

OP acknowledges this... "Unfortunately, using the mean as a test statistic is flawed - it only works when the pre-selection distribution of A and B is identical, at least beyond C." To me the rest of the article is asks the question, "requirement (c) is really strong, is there a way we can use post-selection statistics to determine bias while weakening (c)? what if we tried measuring the post-selection minimum instead of the mean?" Also PG edited his essay to add that disclaimer only after WildUtah's comment, so it's possible that OP hasn't read the updated version.