Turns Out Dubov Was a Genius - The Threat Is Stronger Than The Execution(Nimzowitch)

Everybody went on him -- shouting lie detectors not being scientific but he was 3 steps ahead and apparently knew that Hans would be too scared to take it regardless. Hans only accepted the conditions because he has such an ego that he didn't think he could lose. After losing Hans tried to give multiple different reasons on why he won't take the test which is typical of a person trying to cover something.

Reminds me the famous chess saying by Nimzowitch - The threat is stronger than the execution.