It really doesn't. If they have looked at the photo and decided it's a match, that already contains a lot of information on gender and sex a guard will use. If

It really doesn't. If they have looked at the photo and decided it's a match, that already contains a lot of information on gender and sex a guard will use. If a guard decides there's a mismatch, we're well out into the extremes of the probability distributions. When we compare that to the chance the ID is a good enough fake to pass otherwise but bad enough that it doesn't have the gender right and the chance that it's just bureaucratic error, a mandatory genital inspection makes very little sense. And that's before we get to the practical costs of making border guards into dick inspectors. We could hypothetically get to your 50% number by just inspecting everybody's genitals, I guess. Except the false positive rate from turning security guards into medical experts would be through the roof.