The reason can lie in execution: some firms have obtained capabilities that enable them to implement and hence profit from the strategy better than others.
Ms. Lewinsky especially had no reason to lie to Dr. Kassorla and Ms. Estep, to whom she related the facts in the course of a professional relationship.
One of the strategies that experienced police interrogators use is to ask a series of non-threatening questions while observing how the subject behaves when there is no reason to lie.
There's a reason it's so easy to lie to small kids ("Santa really, truly did bring those presents") and that's because they're functional illiterates when it comes to reading inflection and facial expressions.