They are debunked, but they're still intimidating enough to be useful on a lot of people. I have friends who claim to have 'faked out' their poly, and friends who claim they cracked under the pressure and tried to admit everything wrong they'd ever done in their life (not that the examiner cares about throwing a frog at your sister when you were 5). On balance, it's useful for weeding out a certain percentage of people.