I don't disagree. You might see some of the issues with this candidate on what they choose to highlight as their career successes, I've definitely caught dishonest people, or people I wouldn't work with via soft questions.
But I'm not sure, I've never interviewed this person.
I'd bet they could also pass a whiteboard, pair-programming or take-home test too.
That they are willing to lie about it and pass off other's work as their own isn't something that you're going to identify in your typical code interview. Using interrogation tactics to try and weed out the frauds is going to be counter-productive, by driving off all the good candidates.