Something subtle I caught on my 100th watch today that may toe the line between movie detail and fan theory as I don't believe it's directly mentioned in the movie, book, or any BTS stuff, and may have just been some accidental thing that happens to fit perfectly:
DPR carries his sword on his right hip, where any left-handed swordsman would. He had no intention of ever beginning a fight with an opponent with his strong arm – he has the certainty of someone who knows he is the best and at his peak.
Meanwhile, Inigo not only has his sword on his left hip, he draws with his right hand right in front of DPR and hands him the sword with his right hand.
Roberts knew before they ever began that Inigo underestimated him and gave away immediately that Inigo was someone with exceptional skill willing to handicap himself in order to have a more competitive swordfight.
Inigo may canonically be the better swordsman, but he could never defeat someone with such a critical tactical upperhand.
by TheLameSauce