If the method is known -- and it's now very, very widely known by anyone who might want to get past it -- then it's essentially useless; any actual terrorists will practice until they have a high chance of getting through any questions thrown at them.
They can't. Each question requires an answer with specific details, and the number of details required to successfully field any question increases exponentially with the number of questions. Nobody, no matter how much training he has, can memorize enough detail in advance to consistently and plausibly answer every question he will be asked when interrogated in this way. That's why it works. It works even when the bad guys know the method themselves in detail.
This screening method has been used in some parts of the world for years in aviation, and has been very widely used by law enforcement and military interrogators for a much longer time. Its drawbacks are that it requires a skilled practitioner and time, but it works extremely well.
Screening methods that concentrate on looking for
things,, instead of looking at
people, are ridiculously inadequate in comparison.
In addition, psychopaths are extremely good liars to begin with and probably make up a far larger proportion of the potential recruits for a terrorist group than they do in the general population.
Psychopaths are typically far too interested in themselves to care about working for a terrorist group. It is true that they can lie without visible signs of stress in many cases, but they will still betray themselves in a deep interrogation, just like anyone else who is trying to lie.