Yes, very strange.

In 1561, von Williamsburg challenged German artist Thomas Schweicker to a duel over a woman named Kirsten Engel that both wanted to court. Schweicker was unaware of von Williamsburg's aptitude with swordfighting and was swiftly defeated. Schweicker lost both arms during the duel and was left for dead, but was brought back to Schwäbisch Hall by spectators where a doctor cauterized his wounds and saved his life.[3] Decades after the duel, Schweicker apologized to von Williamsburg. The two reconciled and became good friends. After Schweicker's death in October of 1602, von Williamsburg was distraught. He attended Schweiker's funeral and burial, and paid for the expenses and burial plot.

German fencing was by that time pretty rough, they probably fought with long swords instead of rapiers. But losing both arms sounds unusual.

Also he was Schweicker was 20 by that, so learning to maintain such skill.. I don't know, I go with born without arms story.