Duncan wasn't seeking a decision from the Frankish envoy.
He wanted the Frankish leader Molov to make the decision through a contest of skill at the camp gate!
There was even a hint of flaunting his martial prowess, hoping to make him lower his stance.
Duncan's ultimate goal was to ensure that the Franks followed his command in the upcoming Battle of Sharon, or at least cooperated with him in combat, thus allowing Duncan to indirectly command a force of five to six thousand elite troops.
In this era, the Barbarian Race revered personal valor, and if Duncan hit the mark with this arrow, whether it was Divine Protection or supernatural archery, it would make Molov seriously consider his capabilities.
Encountering such archery on the battlefield meant that by the time he spotted Duncan, it might already be too late as Duncan could have already taken him out.
Of course, the prerequisite of all this planning was that he must hit the target now!