It should be obvious that the sword doesn't test how well your plans correspond to what you think you want! Otherwise Hirou would have been vaporized.

Only assuming that the sword is impulsive. If you take into account Hirou's overall role in the events, this role could be judged good, if only by the final decision.

If the sword judges not plans, but preference, then failing 9 out of 10 people means that it's pretty selective among humans and probably people it selects and their values aren't representative (act in the interests) of the humanity as whole.