It's a two-parter. One, you only give the hardball problems to people you want to filter out, as the paper mentions. Two, you use hardball problems with a sim

It's a two-parter. One, you only give the hardball problems to people you want to filter out, as the paper mentions. Two, you use hardball problems with a simple solution, so that if people make a scandal / complain to political authorities, you can point to the simple solution and "No, look, it's actually really easy, these people just weren't good enough!".