This heart inquisition was indeed as the captain had said. It was another way for the Sword Holder to make an oath.
In front of the emperor, they would answer the questions asked by the emperor's statue. This process was to verify their race as well as to test their temperament.
It wasn't important because even if they didn't pass, it wouldn't affect them from becoming a Sword Holder.
However, it was important because the light from the heart inquisition was the hidden condition for all the future advancements and selections, especially anything that concerned the core of the human race.
It wasn't that this process couldn't be faked, but first, you had to have the ability to deceive the emperor's statue.