(Yes, most of my post probably will be about dueling. Why do you ask )
Anyone who knows me knows that I go into a rant on how the L5R public has a terrible habit of confusing Dueling, Iaijutsu, and Iajutsu dueling as all being the same thing. And I do like how the dueling rules are context free and even have battlefield options in the form of clashes. That being said, I do not see anything in the book detailing how Formal duels of honor should be settled with a formal Iajutsu Duel.
Mostly this could be clarified with some lore text that I am sure will be in the final product, but if Iaijutsu is a Kata that not everyone knows (and also does nothing in of itself to help with a duel mechanically for some reason) then I dont know how it would be represented in a lore fashion.
Again, I LOVE the expansion of dueling outside of the rigid context of honor duels (where most of them realistically would be anyways) but there seems to be a massive lore glitch here when it comes to formally conducting a sanctioned duel of honor.