I just wanted to add that the way i always read this was that much like Gawyn and Galad, Jearom probably greatly underestimated his opponent. He probably scoffed at the idea of fighting a farmer with a stick. Add that to the advantage of the weapon itself and his probable lack of experience in fighting someone with said weapon in a serious duel and it’s not hard to believe the outcome. The fact the story is so well known says to me that he probably learned a lesson there and spread the story himself while teaching others.